For the genus, see Bacillus. This page is about the bacterial genus For the class see Bacilli.

Bacteria Fossil range: Archean or earlier - Recent
Escherichia coli cells magnified 25,000 times
Scientific classification
Domain: Bacteria
Phyla
Acidobacteria Actinobacteria Aquificae Bacteroidetes Chlamydiae Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia

Bacteria (singular: bacterium) are unicellular microorganisms. Acidobacteria are a newly devised Phylum of Bacteria. As implied by their name they are acidophilic and were first recognized as a novel division in Actinobacteria or actinomycetes are a group of Gram-positive bacteria with high G+C ratio. The Aquificae phylum is a diverse collection of bacteria that live in harsh environmental settings The phylum Bacteroidetes is composed of three large classes of Bacteria that are widely distributed in the environment including in soil in sediments sea water Chlamydiae is a Bacterial phylum and class whose members are obligate intracellular pathogens The green sulfur bacteria are a family of obligately anaerobic Photoautotrophic bacteria. Chrysiogenes arsenatis is a species of Bacterium given its own phylum called the Chrysiogenetes. Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of Bacteria that obtain their energy The Deferribacteraceae are a family of bacteria, given their own phylum (Deferribacteres The Deinococcus-Thermus are a small group of bacteria comprised of Cocci highly resistant to environmental hazards Dictyoglomus thermophilum is a species of Bacterium, given its own phylum called the Dictyoglomi Fibrobacteres is a small Bacterial phylum which includes many of the major Rumen bacteria allowing for the degradation of plant-based Cellulose The Firmicutes ( Latin: firmus, strong and cutis, skin referring to the cell wall are a division of bacteria, most of which have Gram-positive Fusobacterium is a genus of filamentous anaerobic, Gram-negative bacteria similar to Bacteroides. The Gemmatimonadetes are a family of bacteria, given their own Phylum (Gemmatimonadetes The Nitrospira are a family of bacteria, given their own phylum (Nitrospirae Planctomycetes are a Phylum of aquatic Bacteria and are found in field samples of brackish, and marine and fresh Water The Proteobacteria are a major group ( Phylum) of Bacteria. They include a wide variety of Pathogens such as Escherichia, Spirochaetes is a phylum of distinctive Gram-negative bacteria, which have long helically coiled cells The Thermodesulfobacteria are a small group of thermophilic Sulfate-reducing bacteria. The Thermomicrobia are a group of Thermophilic green non-sulfur Bacteria. Thermotoga are Thermophile or Hyperthermophile Bacteria whose cell is wrapped in an outer "toga" membrane Verrucomicrobia is a recently described phylum of bacteria. This phylum contains only a few described species ( Verrucomicrobia spinosum, is an example A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods to spirals. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre "Globose" redirects here See also Globose nucleus. A sphere (from Greek σφαίρα - sphaira, "globe Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste,^[1] seawater, and deep in the Earth's crust. A habitat (which is Latin for "it inhabits" is an Ecological or environmental area that is inhabited by a particular Species. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 A hot spring is a spring that is produced by the emergence of geothermally heated Groundwater from the earth's crust. Radioactive wastes are Waste types containing radioactive Chemical elements that do not have a practical purpose In Geology, a crust is the outermost solid shell of a planet or moon There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water; in all, there are approximately five nonillion (5×10³⁰) bacteria on Earth,^[2] forming much of the world's biomass. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Names of numbers larger than a quadrillion are almost never used for reasons discussed further below Biomass, in Ecology, is the mass of living biological organisms in a given area or Ecosystem at a given time ^[3] Bacteria are vital in recycling nutrients, and many important steps in nutrient cycles depend on bacteria, such as the fixation of nitrogen from the atmosphere. In Ecology and Earth science, a biogeochemical cycle is a circuit or pathway by which a Chemical element or Molecule moves through both biotic Nitrogen fixation is the process by which Nitrogen is taken from its natural relatively inert molecular form (N2 in the atmosphere and converted into Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five However, most of these bacteria have not been characterized, and only about half of the phyla of bacteria have species that can be cultured in the laboratory. A phylum ( Plural: phyla) is a Taxonomic rank between Kingdom and above Class. A microbiological culture, AKA microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory A laboratory (informally lab) is a facility that provides controlled conditions in which scientific Research, Experiments and ^[4] The study of bacteria is known as bacteriology, a branch of microbiology. Microbiology (from Greek grc μῑκρος mīkros, "small" grc βίος bios, " Life " and grc -λογία Microbiology (from Greek grc μῑκρος mīkros, "small" grc βίος bios, " Life " and grc -λογία

There are approximately ten times as many bacterial cells as human cells in the human body, with large numbers of bacteria on the skin and in the digestive tract. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus The skin is the outer covering of living tissue of an animal (or plant ^[5] Although the vast majority of these bacteria are rendered harmless by the protective effects of the immune system, and a few are beneficial, some are pathogenic bacteria and cause infectious diseases, including cholera, syphilis, anthrax, leprosy and bubonic plague. An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor Probiotics are Dietary supplements containing potentially beneficial Bacteria or Yeasts According to the currently adopted definition by FAO / Pathogenic bacteria are Bacteria that cause Infectious diseases. An infectious disease is a clinically evident Disease resulting from the presence of Pathogenic microbial agents including Pathogenic viruses Pathogenic Cholera, sometimes known as Asiatic cholera or epidemic cholera, is an infectious Gastroenteritis caused by the Bacterium Syphilis is a Sexually transmitted disease caused by the spirochetal Bacterium Treponema pallidum pallidum. Anthrax is an acute Disease in humans and animals caused by the bacterium Bacillus anthracis which is highly lethal in some forms Leprosy (from the Greek lepi (λέπι meaning scales on a fish or Hansen's disease, is a chronic disease caused by the bacterium Bubonic plague is the best-known manifestation of the bacterial disease plague, caused by the bacterium Yersinia pestis (formerly known as The most common fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people a year, mostly in sub-Saharan Africa. Tuberculosis (abbreviated as TB for tubercle bacillus or T u' b' erculosis Bacillus --> is a common Sub-Saharan Africa is a geographical term used to describe the area of the African continent which lies south of the Sahara, or those African countries ^[6] In developed countries, antibiotics are used to treat bacterial infections and in various agricultural processes, so antibiotic resistance is becoming common. The term developed country, or advanced country, is used to categorize countries with developed Economies in which the tertiary and quaternary sectors In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa Antibiotic resistance is the ability of a Microorganism to withstand the effects of Antibiotics. In industry, bacteria are important in processes such as sewage treatment, the production of cheese and yoghurt, and the manufacture of antibiotics and other chemicals. Sewage treatment, or domestic wastewater treatment, is the process of removing Contaminants from Wastewater, both Runoff ( Effluents Cheese is a Food made from Milk, usually the milk of cows, Buffalo, Goats or sheep, by coagulation. Yoghurt, yogurt, yoghourt, youghurt or yogourt (see spelling below is a ^[7]

Bacteria are prokaryotes. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and rarely harbour membrane-bound organelles. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer In Cell biology, an organelle (pronunciation /ɔː(rgəˡnɛl/ is a specialized subunit within a cell that has a specific function and is usually separately enclosed Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotic life consists of two very different groups of organisms that evolved independently from an ancient common ancestor. eVolution is the third Album by eLDee, it was due to be released in 2008 These evolutionary domains are called Bacteria and Archaea. In biological Taxonomy, a domain (also superregnum, superkingdom, or empire) is the highest Taxonomic rank of Organisms ^[8]

Contents 1 History of bacteriology 2 Origin and early evolution 3 Morphology 4 Cellular structure 4.1 Intracellular structures 4.2 Extracellular structures 4.3 Endospores 5 Metabolism 6 Growth and reproduction 7 Genetics 8 Movement 9 Classification and identification 10 Interactions with other organisms 10.1 Mutualists 10.2 Pathogens 11 Significance in technology and industry 12 See also 13 References 14 Further reading 15 External links

History of bacteriology

Further information: Microbiology

Bacteria were first observed by Antonie van Leeuwenhoek in 1676, using a single-lens microscope of his own design. Antonie Philips van Leeuwenhoek (October 24 1632 &ndash August 30 1723 was a Dutch tradesman and Scientist from Delft, the Netherlands A microscope ( Greek: ( micron) = small + ( skopein) = to look or see is an instrument for viewing objects that are ^[9] He called them "animalcules" and published his observations in a series of letters to the Royal Society. The Royal Society of London for the Improvement of Natural Knowledge, known simply as The Royal Society, is a Learned society for science that was founded in 1660 ^[10][11][12] The name bacterium was introduced much later, by Christian Gottfried Ehrenberg in 1838, and is derived from the Greek word βακτήριον -α , bacterion -a , meaning "small staff". Christian Gottfried Ehrenberg ( April 19, 1795 &ndash June 27, 1876) German naturalist, Zoologist, Comparative This is a list of Greek words with derivatives in English (and other modern languages ^[13]

Louis Pasteur demonstrated in 1859 that the fermentation process is caused by the growth of microorganisms, and that this growth is not due to spontaneous generation. Louis Pasteur (27 December 1822 – 28 September 1895 a French Chemist and Microbiologist, is best known for remarkable breakthroughs in the causes and Fermentation in Food processing typically refers to the conversion of Sugar to Alcohol using Yeast under Anaerobic conditions In the Natural sciences, Abiogenesis, or origin of life, is the study of how Life on Earth emerged from Inanimate Organic (Yeasts and molds, commonly associated with fermentation, are not bacteria, but rather fungi. Yeasts are a growth form of eukaryotic Microorganisms classified in the kingdom Fungi, with about 1500 Species currently described WikipediaManual_of_Style#National_varieties_of_English --> Molds (or A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ ) Along with his contemporary, Robert Koch, Pasteur was an early advocate of the germ theory of disease. Heinrich Hermann Robert Koch ( December 11 1843 – May 27 1910) was a German Physician. The germ theory, also called the pathogenic theory of medicine, is a Theory that proposes that Microorganisms are the cause of many Diseases. ^[14] Robert Koch was a pioneer in medical microbiology and worked on cholera, anthrax and tuberculosis. Cholera, sometimes known as Asiatic cholera or epidemic cholera, is an infectious Gastroenteritis caused by the Bacterium Anthrax is an acute Disease in humans and animals caused by the bacterium Bacillus anthracis which is highly lethal in some forms Tuberculosis (abbreviated as TB for tubercle bacillus or T u' b' erculosis Bacillus --> is a common In his research into tuberculosis, Koch finally proved the germ theory, for which he was awarded a Nobel Prize in 1905. The Nobel Prize in Physiology or Medicine (Nobelpriset i fysiologi eller medicin is awarded once a year by the Swedish Karolinska Institute. ^[15] In Koch's postulates, he set out criteria to test if an organism is the cause of a disease; these postulates are still used today. Koch's postulates are four criteria designed to establish a causal relationship between a causative Microbe and a Disease. A disease is an abnormal condition of an organism that impairs bodily functions and can be deadly ^[16]

Though it was known in the nineteenth century that bacteria are the cause of many diseases, no effective antibacterial treatments were available. Antiseptics (from Greek αντί - anti, '"against" + σηπτικός - septikos, "putrefactive" are antimicrobial ^[17] In 1910, Paul Ehrlich developed the first antibiotic, by changing dyes that selectively stained Treponema pallidum—the spirochaete that causes syphilis—into compounds that selectively killed the pathogen. Paul Ehrlich ( March 14, 1854 &ndash August 20, 1915) was a German Scientist who won the 1908 Nobel Treponema pallidum is a Gram-negative Spirochaete Bacterium. There are at least four known Subspecies: T Spirochaetes is a phylum of distinctive Gram-negative bacteria, which have long helically coiled cells Syphilis is a Sexually transmitted disease caused by the spirochetal Bacterium Treponema pallidum pallidum. ^[18] Ehrlich had been awarded a 1908 Nobel Prize for his work on immunology, and pioneered the use of stains to detect and identify bacteria, with his work being the basis of the Gram stain and the Ziehl-Neelsen stain. Immunology is a broad branch of biomedical Science that covers the study of all aspects of the Immune system in all Organisms It deals with Gram staining (or Gram's method) is an empirical method of differentiating bacterial species into two large groups ( Gram-positive and The Ziehl-Neelsen stain, also known as the acid-fast stain, was first described by two German doctors Franz Ziehl (1859 to 1926 a bacteriologist and Friedrich ^[19]

A major step forward in the study of bacteria was the recognition in 1977 by Carl Woese that archaea have a separate line of evolutionary descent from bacteria. Carl Richard Woese (born July 15 1928, Syracuse New York) is an American Microbiologist who attended Deerfield Academy ^[20] This new phylogenetic taxonomy was based on the sequencing of 16S ribosomal RNA, and divided prokaryotes into two evolutionary domains, as part of the three-domain system. Taxonomy is the practice and science of classification The word comes from the Greek, taxis (meaning 'order' 'arrangement' and, nomos For the sense of "sequencing" used in Electronic music, see the Music sequencer article The three-domain system is a Biological classification introduced by Carl Woese in 1990 that divides cellular life forms into Archaea, ^[21]

Origin and early evolution

Further information: Timeline of evolution

The ancestors of modern bacteria were single-celled microorganisms that were the first forms of life to develop on earth, about 4 billion years ago. This timeline of the evolution of life outlines the major events in the development In the Natural sciences, Abiogenesis, or origin of life, is the study of how Life on Earth emerged from Inanimate Organic For about 3 billion years, all organisms were microscopic, and bacteria and archaea were the dominant forms of life. ^[22][23] Although bacterial fossils exist, such as stromatolites, their lack of distinctive morphology prevents them from being used to examine the past history of bacterial evolution, or to date the time of origin of a particular bacterial species. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Stromatolites (from Greek στρώμα strōma, mattress bed stratum and λιθος lithos, rock are layered accretionary Structures formed in The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism However, gene sequences can be used to reconstruct the bacterial phylogeny, and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. ^[24] The most recent common ancestor of bacteria and archaea was probably a hyperthermophile that lived about 2. In Genetics, the most recent common ancestor ( MRCA) of any set of Organisms is the most recent individual from which all organisms in the group are directly A thermophile is an organism &mdash a type of Extremophile &mdash which thrives at relatively high temperatures between 45 and 80 °C (113 and 176 °F 5 billion–3. 2 billion years ago. ^[25][26]

Bacteria were also involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from ancient bacteria entering into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea. An endosymbiont is any Organism that lives within the body or cells of another organism i ^[27][28] This involved the engulfment by proto-eukaryotic cells of alpha-proteobacterial symbionts to form either mitochondria or hydrogenosomes, which are still being found in all known Eukarya (sometimes in highly reduced form, e. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. A hydrogenosome is a membrane-enclosed Organelle of some anaerobic Ciliates trichomonads and Fungi. g. in ancient "amitochondrial" protozoa). Later on, an independent second engulfment by some mitochondria-containing eukaryotes of cyanobacterial-like organisms led to the formation of chloroplasts in algae and plants. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. There are even some algal groups known that clearly originated from subsequent events of endosymbiosis by heterotrophic eukaryotic hosts engulfing a eukaryotic algae that developed into "second-generation" plastids. ^[29][30]

Morphology

Bacteria display a wide diversity of shapes and sizes, called morphologies. The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism Bacterial cells are about one tenth the size of eukaryotic cells and are typically 0. 5–5. 0 micrometres in length. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre However, a few species–for example Thiomargarita namibiensis and Epulopiscium fishelsoni–are up to half a millimetre long and are visible to the unaided eye. Thiomargarita namibiensis ("Sulfur pearl of Namibia " is a Gram-negative Coccus Proteobacterium found in the ocean sediments Epulopiscium fishelsoni ("Fishelson's guest at a fish's banquet" is a Gram-positive bacterium that has a symbiotic relationship The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to ^[31] Among the smallest bacteria are members of the genus Mycoplasma, which measure only 0. Mycoplasma is a Genus of bacteria which lack a Cell wall. Without a cell wall they are unaffected by many common Antibiotics such 3 micrometres, as small as the largest viruses. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable ^[32]

Most bacterial species are either spherical, called cocci (sing. Staphylococcus aureus Gramjpg|thumb|300px| Staphylococcus bacteria]] Cocci (singular - coccus, from the Latin coccinus (scarlet and derived from the coccus, from Greek kókkos, grain, seed) or rod-shaped, called bacilli (sing. This page is about the bacterial genus For the class see Bacilli. bacillus, from Latin baculus, stick). Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Some rod-shaped bacteria, called vibrio, are slightly curved or comma-shaped; others, can be spiral-shaped, called spirilla, or tightly coiled, called spirochaetes. Vibrio is a Genus of Gram-negative Bacteria possessing a curved rod shape Spirillum in Microbiology refers to a Bacterium with a cell body that twists like a spiral Spirochaetes is a phylum of distinctive Gram-negative bacteria, which have long helically coiled cells A small number of species even have tetrahedral or cuboidal shapes. ^[33] This wide variety of shapes is determined by the bacterial cell wall and cytoskeleton, and is important because it can influence the ability of bacteria to acquire nutrients, attach to surfaces, swim through liquids and escape predators. A cell wall is a tough flexible and sometimes fairly rigid layer surrounding a cell, located external to the Cell membrane, which provides the cell with structural cytoskeleton (also CSK is a cellular " Scaffolding " or " Skeleton " contained within the Cytoplasm. ^[34][35]

Many bacterial species exist simply as single cells, others associate in characteristic patterns: Neisseria form diploids (pairs), Streptococcus form chains, and Staphylococcus group together in "bunch of grapes" clusters. Neisseria is a genus of Gram (- bacteria included among the Proteobacteria, a large group of Gram-negative forms Streptococcus is a Genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the Staphylococcus (in Greek σταφυλη staphyle means bunch of grapes and κοκκος coccos means granule is a genus of Gram-positive Bacteria can also be elongated to form filaments, for example the Actinobacteria. Actinobacteria or actinomycetes are a group of Gram-positive bacteria with high G+C ratio. Filamentous bacteria are often surrounded by a sheath that contains many individual cells; certain types, such as species of the genus Nocardia, even form complex, branched filaments, similar in appearance to fungal mycelia. Nocardia is a Genus of Gram-positive, catalase-positive, rod-shaped Bacteria. Mycelium (plural mycelia) is the vegetative part of a Fungus, consisting of a mass of branching thread-like Hyphae The mass of hyphae is sometimes called ^[36]

Bacteria often attach to surfaces and form dense aggregations called biofilms or bacterial mats. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other A biomolecule is any organic Molecule that is produced by living Organisms including large Polymeric molecules such as Proteins A biofilm is a structured community of Microorganisms encapsulated within a self-developed polymeric matrix and adherent to a living or inert surface A bacterial mat is a layer of Bacteria that may form in environments where other organisms are unable to thrive (e These films can range from a few micrometers in thickness to up to half a meter in depth, and may contain multiple species of bacteria, protists and archaea. Protists (ˈproʊtɨst are a diverse group of eukaryotic Microorganisms Historically protists were treated as the kingdom Protista but this Bacteria living in biofilms display a complex arrangement of cells and extracellular components, forming secondary structures such as microcolonies, through which there are networks of channels to enable better diffusion of nutrients. ^[37][38] In natural environments, such as soil or the surfaces of plants, the majority of bacteria are bound to surfaces in biofilms. ^[39] Biofilms are also important for chronic bacterial infections and infections of implanted medical devices, as bacteria protected within these structures are much harder to kill than individual bacteria. An implant is a Medical device made to replace and act as a missing biological structure (as compared with a transplant, which indicates transplanted Biomedical ^[40]

Even more complex morphological changes are sometimes possible. For example, when starved of amino acids, Myxobacteria detect surrounding cells in a process known as quorum sensing, migrate towards each other, and aggregate to form fruiting bodies up to 500 micrometres long and containing approximately 100,000 bacterial cells. The myxobacteria (" slime bacteria " are a group of bacteria that predominantly live in the soil Quorum sensing is a type of decision-making process used by decentralized groups to coordinate behavior ^[41] In these fruiting bodies, the bacteria perform separate tasks; this type of cooperation is a simple type of multicellular organisation. Multicellular organisms are Organisms consisting of more than one cell, and having Differentiated cells that perform specialized functions For example, about one in 10 cells migrate to the top of these fruiting bodies and differentiate into a specialised dormant state called myxospores, which are more resistant to desiccation and other adverse environmental conditions than are ordinary cells. In Developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized Cell type. ^[42]

Cellular structure

Further information: Bacterial cell structure

Intracellular structures

The bacterial cell is surrounded by a lipid membrane, or cell membrane, which encompasses the contents of the cell and acts as a barrier to hold nutrients, proteins and other essential components of the cytoplasm within the cell. Bacteria, despite their apparent simplicity contain a well developed cell structure which is responsible for many of their unique biological properties Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. As they are prokaryotes, bacteria do not tend to have membrane-bound organelles in their cytoplasm and thus contain few intracellular structures. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other In Cell biology, an organelle (pronunciation /ɔː(rgəˡnɛl/ is a specialized subunit within a cell that has a specific function and is usually separately enclosed They consequently lack a nucleus, mitochondria, chloroplasts and the other organelles present in eukaryotic cells, such as the Golgi apparatus and endoplasmic reticulum. In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. The Golgi apparatus (also called the The endoplasmic reticulum (Greek endo = "within" (prefix plásma = "formed entity" Latin reticulum = "little net" or ER, is an Organelle ^[43] However, recent research is identifying increasing amounts of structural complexity in bacteria, such as the discovery of the prokaryotic cytoskeleton. The prokaryotic cytoskeleton is the collective name for all structural filaments in Prokaryotes. ^[44][45]

Many important biochemical reactions, such as energy generation, occur due to concentration gradients across membranes, creating a potential difference analogous to a battery. Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement In electronics a battery is a combination of two or more Electrochemical cells which store chemical Energy which can be converted into electrical energy The absence of internal membranes in bacteria means these reactions, such as electron transport, occur across the cell membrane, between the cytoplasm and the periplasmic space. An electron transport chain couples a chemical reaction between an electron donor (such as NADH) and an electron acceptor (such as O2) to the transfer The periplasmic space or periplasm is a space between the inner Cytoplasmic membrane and external Outer membrane of Gram-negative bacteria ^[46] Additionally, while some transporter proteins consume chemical energy, others harness concentration gradients to import nutrients across the cell membrane or to expel undesired molecules from the cytoplasm.

Bacteria do not have a membrane-bound nucleus, and their genetic material is typically a single circular chromosome located in the cytoplasm in an irregularly shaped body called the nucleoid. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance A chromosome is an organized structure of DNA and Protein that is found in cells. In Prokaryotes, the nucleoid (meaning nucleus-like) is an irregularly-shaped region within the cell of Prokaryotes where the Genetic material ^[47] The nucleoid contains the chromosome with associated proteins and RNA. Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units Like all living organisms, bacteria contain ribosomes for the production of proteins, but the structure of the bacterial ribosome is different from those of eukaryotes and Archaea. Ribosomes ( from ribo nucleic acid and "Greek soma ( meaning body") are complexes of RNA and Protein that Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex ^[48] The order Planctomycetes are an exception to the general absence of internal membranes in bacteria, because they have a membrane around their nucleoid and contain other membrane-bound cellular structures. Planctomycetes are a Phylum of aquatic Bacteria and are found in field samples of brackish, and marine and fresh Water ^[49]

Some bacteria produce intracellular nutrient storage granules, such as glycogen,^[50] polyphosphate,^[51] sulfur^[52] or polyhydroxyalkanoates. Glycogen is a Polysaccharide of Glucose (Glc which functions as the secondary short term energy storage in Animal cells Polyphosphates are anionic Phosphate Polymers linked between Hydroxyl groups and Hydrogen atoms Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Polyhydroxyalkanoates or PHA s are linear Polyesters produced in nature by Bacterial fermentation of Sugar or Lipids More ^[53] These granules enable bacteria to store compounds for later use. Certain bacterial species, such as the photosynthetic Cyanobacteria, produce internal gas vesicles, which they use to regulate their buoyancy - allowing them to move up or down into water layers with different light intensities and nutrient levels. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of Bacteria that obtain their energy ^[54]

Extracellular structures

Further information: Cell envelope

Around the outside of the cell membrane is the bacterial cell wall. The cell envelope is the Cell membrane and Cell wall plus an outer membrane if one is present A cell wall is a tough flexible and sometimes fairly rigid layer surrounding a cell, located external to the Cell membrane, which provides the cell with structural Bacterial cell walls are made of peptidoglycan (called murein in older sources), which is made from polysaccharide chains cross-linked by unusual peptides containing D-amino acids. Not to be confused with Glycoprotein. Peptidoglycan, also known as murein, is a Polymer consisting of sugars and amino Polysaccharides are relatively complex Carbohydrates They are Polymers made up of many Monosaccharides joined together by Glycosidic bonds Peptides (from the Greek πεπτίδια, "small digestibles" are short Polymers formed from the linking in a defined order of α- Amino In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this ^[55] Bacterial cell walls are different from the cell walls of plants and fungi, which are made of cellulose and chitin, respectively. Plants are living Organisms belonging to the kingdom Plantae. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Cellulose is an Organic compound with the formula, a Polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4 Chitin ( C 8 H 13 O 5 N)n (ˈkaɪtən is a long-chain Polymer of a N-acetylglucosamine ^[56] The cell wall of bacteria is also distinct from that of Archaea, which do not contain peptidoglycan. The cell wall is essential to the survival of many bacteria, and the antibiotic penicillin is able to kill bacteria by inhibiting a step in the synthesis of peptidoglycan. Penicillin (sometimes abbreviated PCN or pen) is a group of Beta-lactam antibiotics used in the treatment of Bacterial Infections ^[56]

There are broadly speaking two different types of cell wall in bacteria, called Gram-positive and Gram-negative. Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. Gram-negative bacteria are those Bacteria that do not retain Crystal violet dye in the Gram staining protocol The names originate from the reaction of cells to the Gram stain, a test long-employed for the classification of bacterial species. Gram staining (or Gram's method) is an empirical method of differentiating bacterial species into two large groups ( Gram-positive and ^[57]

Gram-positive bacteria possess a thick cell wall containing many layers of peptidoglycan and teichoic acids. Teichoic acids ( cf Greek τειχος teichos "wall" are polymers of glycerol phosphate or ribitol phospate linked via Phosphodiester bonds In contrast, Gram-negative bacteria have a relatively thin cell wall consisting of a few layers of peptidoglycan surrounded by a second lipid membrane containing lipopolysaccharides and lipoproteins. Lipopolysaccharides ( LPS) are large Molecules consisting of a Lipid and a Polysaccharide joined by a Covalent bond; they are found A lipoprotein is a biochemical assembly that contains both Proteins and Lipids The lipids or their derivatives may be covalently or non-covalently bound Most bacteria have the Gram-negative cell wall, and only the Firmicutes and Actinobacteria (previously known as the low G+C and high G+C Gram-positive bacteria, respectively) have the alternative Gram-positive arrangement. The Firmicutes ( Latin: firmus, strong and cutis, skin referring to the cell wall are a division of bacteria, most of which have Gram-positive Actinobacteria or actinomycetes are a group of Gram-positive bacteria with high G+C ratio. ^[58] These differences in structure can produce differences in antibiotic susceptibility; for instance, vancomycin can kill only Gram-positive bacteria and is ineffective against Gram-negative pathogens, such as Haemophilus influenzae or Pseudomonas aeruginosa. Vancomycin ( INN) (ˌvæŋkoʊˈmaɪsɪn is a Glycopeptide Antibiotic used in the Prophylaxis and treatment of infections caused by A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, is a non-motile Gram-negative Coccobacillus Pseudomonas aeruginosa is a Gram-negative, aerobic, rod-shaped Bacterium with unipolar motility. ^[59]

In many bacteria an S-layer of rigidly arrayed protein molecules covers the outside of the cell. An S-layer (surface layer is a part of the Cell envelope commonly found in Bacteria, as well as among Archaea. ^[60] This layer provides chemical and physical protection for the cell surface and can act as a macromolecular diffusion barrier. The term macromolecule by definition implies "large Molecule " S-layers have diverse but mostly poorly understood functions, but are known to act as virulence factors in Campylobacter and contain surface enzymes in Bacillus stearothermophilus. The Genus Campylobacter, (meaning 'twisted bacteria' first discovered in 1963 describes Gram-negative, spiral Microaerophilic bacteria Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Bacillus stearothermophilus (or Geobacillus stearothermophilus) is a rod-shaped Gram-positive Bacterium and a member of the division ^[61]

Flagella are rigid protein structures, about 20 nanometres in diameter and up to 20 micrometres in length, that are used for motility. Helicobacter pylori ( is a Gram-negative, microaerophilic Bacterium that inhabits various areas of the stomach and Duodenum. A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International Flagella are driven by the energy released by the transfer of ions down an electrochemical gradient across the cell membrane. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge In Cellular biology, an electrochemical gradient is a spatial variation of both Electrical potential and chemical Concentration across a membrane ^[62]

Fimbriae are fine filaments of protein, just 2–10 nanometres in diameter and up to several micrometers in length. In Bacteriology, fimbria is a proteinaceous appendage in many Gram-negative bacteria that is thinner and shorter than a Flagellum. They are distributed over the surface of the cell, and resemble fine hairs when seen under the electron microscope. An electron microscope is a type of Microscope that uses Electrons to illuminate a specimen and create an enlarged image Fimbriae are believed to be involved in attachment to solid surfaces or to other cells and are essential for the virulence of some bacterial pathogens. ^[63] Pili (sing. A pilus ( Latin for 'hair' plural: pili) is a hairlike appendage found on the surface of many bacteria. pilus) are cellular appendages, slightly larger than fimbriae, that can transfer genetic material between bacterial cells in a process called conjugation (see bacterial genetics, below). Bacterial conjugation is the transfer of genetic material between bacteria through direct cell-to-cell contact ^[64]

Capsules or slime layers are produced by many bacteria to surround their cells, and vary in structural complexity: ranging from a disorganised slime layer of extra-cellular polymer, to a highly structured capsule or glycocalyx. A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds Capsule in Microbiology refers to a layer that lies outside the Cell wall of bacteria. Glycocalyx is a general term referring to extracellular Polymeric material produced by some Bacteria, Epithelia and other cells These structures can protect cells from engulfment by eukaryotic cells, such as macrophages. Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that ^[65] They can also act as antigens and be involved in cell recognition, as well as aiding attachment to surfaces and the formation of biofilms. ^[66]

The assembly of these extracellular structures is dependent on bacterial secretion systems. Secretion is the process of segregating elaborating and releasing chemicals from a cell, or a secreted Chemical substance or amount of substance These transfer proteins from the cytoplasm into the periplasm or into the environment around the cell. Many types of secretion systems are known and these structures are often essential for the virulence of pathogens, so are intensively studied. Virulence (also called pestiferousness) refers to the degree of Pathogenicity of a Microbe, or in other words the relative ability of a Microbe ^[67]

Endospores

Further information: Endospores

Certain genera of Gram-positive bacteria, such as Bacillus, Clostridium, Sporohalobacter, Anaerobacter and Heliobacterium, can form highly resistant, dormant structures called endospores. An endospore is a dormant, tough and non-reproductive structure produced by a small number of Bacteria from the Firmicute phylum Bacillus anthracis is a Gram-positive, facultatively anaerobic, rod-shaped Bacterium of the genus Bacillus. Cerebrospinal fluid ( CSF) Liquor cerebrospinalis, is a clear Bodily fluid that occupies the Subarachnoid space and the Ventricular system A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic This page is about the bacterial genus For the class see Bacilli. Clostridium is a Genus of Gram-positive bacteria belonging to the Firmicutes. Sporohalobacter are a genus of anaerobic Bacteria belonging to the family Haloanaerobiaceae Anaerobacter are a genus of Gram-positive Bacteria related to Clostridium. The heliobacteria are phototrophic that is to say they convert light energy into chemical energy by photosynthesis they use a PSI type reaction center An endospore is a dormant, tough and non-reproductive structure produced by a small number of Bacteria from the Firmicute phylum ^[68] In almost all cases, one endospore is formed and this is not a reproductive process, although Anaerobacter can make up to seven endospores in a single cell. Anaerobacter are a genus of Gram-positive Bacteria related to Clostridium. ^[69] Endospores have a central core of cytoplasm containing DNA and ribosomes surrounded by a cortex layer and protected by an impermeable and rigid coat. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Ribosomes ( from ribo nucleic acid and "Greek soma ( meaning body") are complexes of RNA and Protein that

Endospores show no detectable metabolism and can survive extreme physical and chemical stresses, such as high levels of UV light, gamma radiation, detergents, disinfectants, heat, pressure and desiccation. Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions A detergent (as a noun is a material intended to assist Cleaning. Disinfectants are Antimicrobial agents that are applied to non-living objects to destroy Microorganisms, the process of which is known as disinfection. Desiccation is the state of extreme dryness or the process of extreme drying ^[70] In this dormant state, these organisms may remain viable for millions of years,^[71][72] and endospores even allow bacteria to survive exposure to the vacuum and radiation in space. This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. ^[73] Endospore-forming bacteria can also cause disease: for example, anthrax can be contracted by the inhalation of Bacillus anthracis endospores, and contamination of deep puncture wounds with Clostridium tetani endospores causes tetanus. Anthrax is an acute Disease in humans and animals caused by the bacterium Bacillus anthracis which is highly lethal in some forms Bacillus anthracis is a Gram-positive, facultatively anaerobic, rod-shaped Bacterium of the genus Bacillus. Clostridium tetani is a rod-shaped anaerobic Bacterium of the genus Clostridium. Tetanus is a medical condition that is characterized by a prolonged contraction of Skeletal muscle fibres ^[74]

Metabolism

Further information: Microbial metabolism

In contrast to higher organisms, bacteria exhibit an extremely wide variety of metabolic types. Microbial metabolism is the means by which a Microbe obtains the energy and nutrients (e Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of Bacteria that obtain their energy Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. ^[75] The distribution of metabolic traits within a group of bacteria has traditionally been used to define their taxonomy, but these traits often do not correspond with modern genetic classifications. Taxonomy is the practice and science of classification The word comes from the Greek, taxis (meaning 'order' 'arrangement' and, nomos ^[76] Bacterial metabolism is classified on the basis of three major criteria: the kind of energy used for growth, the source of carbon, and the electron donors used for growth. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 An electron donor is a chemical entity that donates Electrons to another compound An additional criterion of respiratory microorganisms are the electron acceptors used for aerobic or anaerobic respiration. An electron acceptor is a chemical entity that accepts Electrons transferred to it from another compound ^[77]

Carbon metabolism in bacteria is either heterotrophic, where organic carbon compounds are used as carbon sources, or autotrophic, meaning that cellular carbon is obtained by fixing carbon dioxide. A heterotrophs, or chemoorganotrophy ( Greek heterone = (another and trophe = nutrition is an Organism that requires An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. An autotroph (from the Greek autos = self and trophe = nutrition is an Organism that produces complex Organic compounds from simple Carbon fixation is a process found in Autotrophs (organisms that produce their own food usually driven by Photosynthesis, whereby Carbon dioxide is changed Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Typical autotrophic bacteria are phototrophic cyanobacteria, green sulfur-bacteria and some purple bacteria, but also many chemolithotrophic species, such as nitrifying or sulfur-oxidising bacteria. Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of Bacteria that obtain their energy Purple bacteria or purple photosynthetic bacteria are Proteobacteria that are Phototrophic i ^[78] Energy metabolism of bacteria is either based on phototrophy, the use of light through photosynthesis, or on chemotrophy, the use of chemical substances for energy, which are mostly oxidised at the expense of oxygen or alternative electron acceptors (aerobic/anaerobic respiration). Photoautotrophs or Phototroph ( Gk: photo = light auto = self troph = nourishment are Organisms (commonly plants that carry out Photosynthesis Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Chemotrophs are organisms that obtain Energy by the Oxidation of Electron donating Molecules in their environments

Finally, bacteria are further divided into lithotrophs that use inorganic electron donors and organotrophs that use organic compounds as electron donors. A lithotroph is an Organism that uses an Inorganic substrate (usually of mineral origin to obtain reducing equivalents for use in biosynthesis (e An organotroph is an organism that obtains hydrogen or electrons from organic substrates Chemotrophic organisms use the respective electron donors for energy conservation (by aerobic/anaerobic respiration or fermentation) and biosynthetic reactions (e. g. carbon dioxide fixation), whereas phototrophic organisms use them only for biosynthetic purposes. Respiratory organisms use chemical compounds as a source of energy by taking electrons from the reduced substrate and transferring them to a terminal electron acceptor in a redox reaction. Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state An electron acceptor is a chemical entity that accepts Electrons transferred to it from another compound Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state This reaction releases energy that can be used to synthesise ATP and drive metabolism. Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy In aerobic organisms, oxygen is used as the electron acceptor. An aerobic organism or aerobe is an Organism that has an Oxygen based Metabolism. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the In anaerobic organisms other inorganic compounds, such as nitrate, sulfate or carbon dioxide are used as electron acceptors. An anaerobic organism is any Organism that does not require Oxygen for growth and may even die in its presence In Inorganic chemistry, a nitrate is a salt of Nitric acid with an Ion composed of one Nitrogen and three Oxygen atoms This leads to the ecologically important processes of denitrification, sulfate reduction and acetogenesis, respectively. Denitrification is a microbially facilitated process of dissimilatory nitrate reduction that may ultimately produce molecular Nitrogen (N2 through a series of intermediate Acetogenesis is a process through which Acetate is produced by Anaerobic bacteria from a variety of energy (for example Hydrogen) and carbon (for example

Another way of life of chemotrophs in the absence of possible electron acceptors is fermentation, where the electrons taken from the reduced substrates are transferred to oxidised intermediates to generate reduced fermentation products (e. g. lactate, ethanol, hydrogen, butyric acid). Lactic acid ( IUPAC Systematic name: 2-hydroxypropanoic acid) also known as milk acid, is a Chemical compound that plays a role Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Butyric acid (from Greek βούτυρος = butter) also known under the systematic name butanoic acid, is a Carboxylic acid with the structural Fermentation is possible, because the energy content of the substrates is higher than that of the products, which allows the organisms to synthesise ATP and drive their metabolism. ^[79][80]

These processes are also important in biological responses to pollution; for example, sulfate-reducing bacteria are largely responsible for the production of the highly toxic forms of mercury (methyl- and dimethylmercury) in the environment. Pollution is the introduction of contaminants into an environment that causes instability disorder harm or discomfort to the physical systems or living organisms they are in Sulfate-reducing bacteria comprise several groups of bacteria that use Sulfate as an oxidizing agent reducing it to Sulfide. Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum Methylmercury (sometimes methyl mercury) is an Organometallic Cation with the formula + Dimethylmercury (( C[[Hydrogen H]]32 Hg) is a flammable colorless liquid and one of the strongest known Neurotoxins It is described ^[81] Non-respiratory anaerobes use fermentation to generate energy and reducing power, secreting metabolic by-products (such as ethanol in brewing) as waste. Fermentation is the process of deriving energy from the oxidation of organic compounds such as carbohydrates using an endogenous electron acceptor which is Facultative anaerobes can switch between fermentation and different terminal electron acceptors depending on the environmental conditions in which they find themselves. A facultative anaerobic organism is an Organism, usually a Bacterium, that makes ATP by Aerobic respiration if Oxygen is present An electron acceptor is a chemical entity that accepts Electrons transferred to it from another compound

Lithotrophic bacteria can use inorganic compounds as a source of energy. Common inorganic electron donors are hydrogen, carbon monoxide, ammonia (leading to nitrification), ferrous iron and other reduced metal ions, and several reduced sulfur compounds. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Nitrification is the biological oxidation of Ammonia with oxygen into Nitrite followed by the oxidation of these nitrites into Nitrates Degradation Iron(II oxide, also known as ferrous oxide, iron oxide/oxidized iron or more commonly rusted Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Unusually, the gas methane can be used by methanotrophic bacteria as both a source of electrons and a substrate for carbon anabolism. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Methanotrophs are bacteria that are able to grow using Methane as their only source of Carbon and Energy. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J ^[82] In both aerobic phototrophy and chemolithotrophy, oxygen is used as a terminal electron acceptor, while under anaerobic conditions inorganic compounds are used instead. A lithotroph is an Organism that uses an Inorganic substrate (usually of mineral origin to obtain reducing equivalents for use in biosynthesis (e Most lithotrophic organisms are autotrophic, whereas organotrophic organisms are heterotrophic.

In addition to fixing carbon dioxide in photosynthesis, some bacteria also fix nitrogen gas (nitrogen fixation) using the enzyme nitrogenase. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Nitrogen fixation is the process by which Nitrogen is taken from its natural relatively inert molecular form (N2 in the atmosphere and converted into Nitrogenase ( is the Enzyme used by some organisms to fix atmospheric Nitrogen gas (N2 This environmentally important trait can be found in bacteria of nearly all the metabolic types listed above, but is not universal. ^[83]

Growth and reproduction

Further information: Bacterial growth

Unlike multicellular organisms, increases in the size of bacteria (cell growth) and their reproduction by cell division are tightly linked in unicellular organisms. Bacterial growth is the division of one Bacterium into two idential daughter cells during a process called Binary fission. The term cell growth is used in two different ways in Biology. Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. Bacteria grow to a fixed size and then reproduce through binary fission, a form of asexual reproduction. Binary fission is the form of Asexual reproduction and Cell division used by Prokaryotic organisms (such as Bacteria or Archea) Asexual reproduction is a form of reproduction which does not involve Meiosis, Ploidy reduction or Fertilization. ^[84] Under optimal conditions, bacteria can grow and divide extremely rapidly, and bacterial populations can double as quickly as every 9. 8 minutes. ^[85] In cell division, two identical clone daughter cells are produced. Molecular cloning refers to the procedure of isolating a defined DNA sequence and obtaining multiple copies of it In vivo. Some bacteria, while still reproducing asexually, form more complex reproductive structures that help disperse the newly-formed daughter cells. Examples include fruiting body formation by Myxobacteria and arial hyphae formation by Streptomyces, or budding. The myxobacteria (" slime bacteria " are a group of bacteria that predominantly live in the soil A hypha (plural hyphae) is a long branching filamentous cell of a Fungus, and also of unrelated Actinobacteria. Streptomyces, the largest Genus of Actinobacteria and type genus of the family Streptomycetaceae. Budding involves a cell forming a protrusion that breaks away and produces a daughter cell.

In the laboratory, bacteria are usually grown using solid or liquid media. Solid growth media such as agar plates are used to isolate pure cultures of a bacterial strain. An agar plate is a sterile Petri dish that contains a Growth medium (typically Agar plus nutrients used to culture Microorganisms However, liquid growth media are used when measurement of growth or large volumes of cells are required. Growth in stirred liquid media occurs as an even cell suspension, making the cultures easy to divide and transfer, although isolating single bacteria from liquid media is difficult. The use of selective media (media with specific nutrients added or deficient, or with antibiotics added) can help identify specific organisms. ^[87]

Most laboratory techniques for growing bacteria use high levels of nutrients to produce large amounts of cells cheaply and quickly. However, in natural environments nutrients are limited, meaning that bacteria cannot continue to reproduce indefinitely. This nutrient limitation has led the evolution of different growth strategies (see r/K selection theory). In Ecology, r/K selection theory relates to the selection of traits which promote success in particular environments Some organisms can grow extremely rapidly when nutrients become available, such as the formation of algal (and cyanobacterial) blooms that often occur in lakes during the summer. An algal bloom is a rapid increase in the population of Algae in an aquatic system ^[88] Other organisms have adaptations to harsh environments, such as the production of multiple antibiotics by Streptomyces that inhibit the growth of competing microorganisms. In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa Streptomyces, the largest Genus of Actinobacteria and type genus of the family Streptomycetaceae. ^[89] In nature, many organisms live in communities (e. g. biofilms) which may allow for increased supply of nutrients and protection from environmental stresses. A biofilm is a structured community of Microorganisms encapsulated within a self-developed polymeric matrix and adherent to a living or inert surface ^[39] These relationships can be essential for growth of a particular organism or group of organisms (syntrophy). Syntrophy is the phenomenon that one species lives off the products of another species ^[90]

Bacterial growth follows three phases. Bacterial growth is the division of one Bacterium into two idential daughter cells during a process called Binary fission. When a population of bacteria first enter a high-nutrient environment that allows growth, the cells need to adapt to their new environment. The first phase of growth is the lag phase, a period of slow growth when the cells are adapting to the high-nutrient environment and preparing for fast growth. Incubation period is the Time elapsed between exposure to a Pathogenic Organism, or Chemical or radiation, and when Symptoms The lag phase has high biosynthesis rates, as proteins necessary for rapid growth are produced. ^[91] The second phase of growth is the logarithmic phase (log phase), also known as the exponential phase. In Mathematics, the logarithm of a number to a given base is the power or Exponent to which the base must be raised in order to produce The log phase is marked by rapid exponential growth. Exponential growth (including Exponential decay) occurs when the growth rate of a mathematical function is proportional to the function's current value The rate at which cells grow during this phase is known as the growth rate (k), and the time it takes the cells to double is known as the generation time (g). During log phase, nutrients are metabolised at maximum speed until one of the nutrients is depleted and starts limiting growth. The final phase of growth is the stationary phase and is caused by depleted nutrients. The cells reduce their metabolic activity and consume non-essential cellular proteins. The stationary phase is a transition from rapid growth to a stress response state and there is increased expression of genes involved in DNA repair, antioxidant metabolism and nutrient transport. DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome. An antioxidant is a Molecule capable of slowing or preventing the oxidation of other molecules Active transport is the mediated process of moving particles across Biological membrane against the concentration gradient ^[92]

Genetics

Further information: Plasmid, Genome

Most bacteria have a single circular chromosome that can range in size from only 160,000 base pairs in the endosymbiotic bacteria Candidatus Carsonella ruddii,^[93] to 12,200,000 base pairs in the soil-dwelling bacteria Sorangium cellulosum. A plasmid is an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently of the chromosomal DNA In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby A chromosome is an organized structure of DNA and Protein that is found in cells. In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called An endosymbiont is any Organism that lives within the body or cells of another organism i Candidatus Carsonella ruddii is an endosymbiotic Gamma Proteobacteria; it has the smallest Genome of any characterised bacteria Sorangium cellulosum is a soil-dwelling Gram-negative Bacteria of the group Myxobacteria. ^[94] Spirochaetes of the genus Borrelia are a notable exception to this arrangement, with bacteria such as Borrelia burgdorferi, the cause of Lyme disease, containing a single linear chromosome. Spirochaetes is a phylum of distinctive Gram-negative bacteria, which have long helically coiled cells A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic See also Lyme disease microbiology Borrelia burgdorferi is species of Bacteria of the spirochete class of the Genus Lyme disease, or borreliosis, is an Emerging infectious disease caused by at least three Species of Bacteria belonging to the Genus ^[95] The genes in bacterial genomes are usually a single continuous stretch of DNA and although several different types of introns do exist in bacteria, these are much more rare than in eukaryotes. Introns, derived from the term "intragenic regions" and also called intervening sequence (IVS are DNA regions in a Gene that are not translated into ^[96]

Bacteria may also contain plasmids, which are small extra-chromosomal DNAs that may contain genes for antibiotic resistance or virulence factors. A plasmid is an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently of the chromosomal DNA Antibiotic resistance is the ability of a Microorganism to withstand the effects of Antibiotics. Virulence (also called pestiferousness) refers to the degree of Pathogenicity of a Microbe, or in other words the relative ability of a Microbe Another type of bacterial DNA are integrated viruses (bacteriophages). Lysogeny, or the lysogenic cycle, is one of two methods of viral reproduction (the Lytic cycle is the other This article is about a biological infectious particle for other uses see Phage (disambiguation. Many types of bacteriophage exist, some simply infect and lyse their host bacteria, while others insert into the bacterial chromosome. lytic cycle is one of the two cycles of viral Reproduction, the other being the Lysogenic cycle. In Biology, a host is an organism that harbors a Virus or Parasite, or a mutual or Commensal Symbiont, typically providing nourishment A bacteriophage can contain genes that contribute to its host's phenotype: for example, in the evolution of Escherichia coli O157:H7 and Clostridium botulinum, the toxin genes in an integrated phage converted a harmless ancestral bacteria into a lethal pathogen. A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties Escherichia coli O157H7 is an Enterohemorrhagic strain of the bacterium Escherichia coli and a cause of Foodborne illness Clostridium botulinum is a Gram-positive, rod shaped bacterium that produces the Neurotoxin Botulin, which causes the flaccid A toxin ( Greek:, toxikon, lit (poison for use on arrows is a Poisonous substance produced by living cells or organisms that is active at very low ^[97]

Bacteria, as asexual organisms, inherit identical copies of their parent's genes (i. e. , they are clonal). Molecular cloning refers to the procedure of isolating a defined DNA sequence and obtaining multiple copies of it In vivo. However, all bacteria can evolve by selection on changes to their genetic material DNA caused by genetic recombination or mutations. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Genetic recombination is the process by which a strand of genetic material (usually DNA; but can also be RNA) is broken and then joined to a different DNA molecule In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism Mutations come from errors made during the replication of DNA or from exposure to mutagens. In Biology, a mutagen ( Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA) Mutation rates vary widely among different species of bacteria and even among different clones of a single species of bacteria. ^[98] Genetic changes in bacterial genomes come from either random mutation during replication or "stress-directed mutation", where genes involved in a particular growth-limiting process have an increased mutation rate. ^[99]

Some bacteria also transfer genetic material between cells. This can occur in three main ways. Firstly, bacteria can take up exogenous DNA from their environment, in a process called transformation. In Molecular biology, transformation is the genetic alteration of a cell resulting from the uptake genomic incorporation and expression of foreign Genes can also be transferred by the process of transduction, when the integration of a bacteriophage introduces foreign DNA into the chromosome. Transduction is the process by which DNA is transferred from one Bacterium to another by a Virus. The third method of gene transfer is bacterial conjugation, where DNA is transferred through direct cell contact. Bacterial conjugation is the transfer of genetic material between bacteria through direct cell-to-cell contact This gene acquisition from other bacteria or the environment is called horizontal gene transfer and may be common under natural conditions. ^[100] Gene transfer is particularly important in antibiotic resistance as it allows the rapid transfer of resistance genes between different pathogens. Antibiotic resistance is the ability of a Microorganism to withstand the effects of Antibiotics. ^[101]

Movement

Further information: Chemotaxis, Flagella, Pilus

Motile bacteria can move using flagella, bacterial gliding, twitching motility or changes of buoyancy. Chemotaxis, a kind of Taxis, is the phenomenon in which bodily cells bacteria, and other single-cell or Multicellular organisms direct their movements A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it A pilus ( Latin for 'hair' plural: pili) is a hairlike appendage found on the surface of many bacteria. A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it Bacterial gliding is a process whereby a Bacterium can move under its own power ^[102] In twitching motility, bacterial use their type IV pili as a grappling hook, repeatedly extending it, anchoring it and then retracting it with remarkable force (>80 pN). A pilus ( Latin for 'hair' plural: pili) is a hairlike appendage found on the surface of many bacteria. The newton (symbol N) is the SI derived unit of Force, named after Isaac Newton in recognition of his work on Classical ^[103]

Bacterial species differ in the number and arrangement of flagella on their surface; some have a single flagellum (monotrichous), a flagellum at each end (amphitrichous), clusters of flagella at the poles of the cell (lophotrichous), while others have flagella distributed over the entire surface of the cell (peritrichous). A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it The bacterial flagella is the best-understood motility structure in any organism and is made of about 20 proteins, with approximately another 30 proteins required for its regulation and assembly. ^[102] The flagellum is a rotating structure driven by a motor at the base that uses the electrochemical gradient across the membrane for power. In Cellular biology, an electrochemical gradient is a spatial variation of both Electrical potential and chemical Concentration across a membrane This motor drives the motion of the filament, which acts as a propeller. Many bacteria (such as E. coli) have two distinct modes of movement: forward movement (swimming) and tumbling. The tumbling allows them to reorient and makes their movement a three-dimensional random walk. A random walk, sometimes denoted RW, is a Mathematical formalization of a trajectory that consists of taking successive Random steps ^[104] (See external links below for link to videos. ) The flagella of a unique group of bacteria, the spirochaetes, are found between two membranes in the periplasmic space. Spirochaetes is a phylum of distinctive Gram-negative bacteria, which have long helically coiled cells They have a distinctive helical body that twists about as it moves. A helix (pl helixes or helices) from the Greek word έλιξ, is a special kind of Space curve, i ^[102]

Motile bacteria are attracted or repelled by certain stimuli in behaviors called taxes: these include chemotaxis, phototaxis and magnetotaxis. In Physiology, a stimulus is a detectable change in the internal or external environment Chemotaxis, a kind of Taxis, is the phenomenon in which bodily cells bacteria, and other single-cell or Multicellular organisms direct their movements Phototaxis is a kind of Taxis that occurs when a whole organism moves in response to the stimulus Light. Magnetotaxis is the ability of certain motile aquatic Bacteria to sense a Magnetic field and coordinate their movement in response (similar to a Tropism ^[105][106] In one peculiar group, the myxobacteria, individual bacteria move together to form waves of cells that then differentiate to form fruiting bodies containing spores. The myxobacteria (" slime bacteria " are a group of bacteria that predominantly live in the soil ^[107] The myxobacteria move only when on solid surfaces, unlike E. The myxobacteria (" slime bacteria " are a group of bacteria that predominantly live in the soil coli which is motile in liquid or solid media. Motility is a biological term which refers to the ability to move spontaneously and actively consuming energy in the process

Several Listeria and Shigella species move inside host cells by usurping the cytoskeleton, which is normally used to move organelles inside the cell. Listeria is a Bacterial Genus containing six species Named in honour of Joseph Lister, Listeria species are Gram-positive This article is about the bacteria For the disease see Shigellosis Shigella is a Genus of Gram-negative cytoskeleton (also CSK is a cellular " Scaffolding " or " Skeleton " contained within the Cytoplasm. In Cell biology, an organelle (pronunciation /ɔː(rgəˡnɛl/ is a specialized subunit within a cell that has a specific function and is usually separately enclosed By promoting actin polymerization at one pole of their cells, they can form a kind of tail that pushes them through the host cell's cytoplasm. Actin is a globular roughly 42-kDa Protein found in all eukaryotic cells (except for Nematode sperm where it may be present at concentrations of Biopolymers are a class of Polymers produced by living organisms ^[108]

Classification and identification

Further information: Scientific classification, Systematics and Clinical pathology

Classification seeks to describe the diversity of bacterial species by naming and grouping organisms based on similarities. Biological systematics is the study of the diversity of Life on the planet Earth both past and present and the relationships among living things through time Pathology; please do not remove --> Laboratory Medicine (Germany Biopathology Bacteria can be classified on the basis of cell structure, cellular metabolism or on differences in cell components such as DNA, fatty acids, pigments, antigens and quinones. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response "DDQ" redirects here DDQ is also the former callsign of a TV station in Toowoomba Queensland Australia ^[87] While these schemes allowed the identification and classification of bacterial strains, it was unclear whether these differences represented variation between distinct species or between strains of the same species. This uncertainty was due to the lack of distinctive structures in most bacteria, as well as lateral gene transfer between unrelated species. ^[109] Due to lateral gene transfer, some closely related bacteria can have very different morphologies and metabolisms. To overcome this uncertainty, modern bacterial classification emphasizes molecular systematics, using genetic techniques such as guanine cytosine ratio determination, genome-genome hybridization, as well as sequencing genes that have not undergone extensive lateral gene transfer, such as the rRNA gene. Guanine is one of the five main Nucleobases found in the Nucleic acids DNA and RNA, the others being Adenine, Cytosine, Cytosine is one of the five main bases found in DNA and RNA. It is a Pyrimidine derivative with a Heterocyclic Aromatic ring GC-content (or guanine-cytosine content in molecular biology is the percentage of Nitrogenous bases on a DNA molecule which are either Guanine or The term DNA sequencing encompasses biochemical methods for determining the order of the Nucleotide bases Adenine, Guanine, Cytosine Ribosomal DNA ( rDNA) are sequences encoding ribosomal RNA. These sequences regulate amplification and transcription initiation and contain transcribed and nontranscribed ^[110] Classification of bacteria is determined by publication in the International Journal of Systematic Bacteriology,^[111] and Bergey's Manual of Systematic Bacteriology. ^[112]

The term "bacteria" was traditionally applied to all microscopic, single-celled prokaryotes. However, molecular systematics showed prokaryotic life to consist of two separate domains, originally called Eubacteria and Archaebacteria, but now called Bacteria and Archaea that evolved independently from an ancient common ancestor. In biological Taxonomy, a domain (also superregnum, superkingdom, or empire) is the highest Taxonomic rank of Organisms ^[113] The archaea and eukaryotes are more closely-related to each other than either is to the bacteria. These two domains, along with Eukarya, are the basis of the three-domain system, which is currently the most widely used classification system in microbiolology. The three-domain system is a Biological classification introduced by Carl Woese in 1990 that divides cellular life forms into Archaea, ^[114] However, due to the relatively recent introduction of molecular systematics and a rapid increase in the number of genome sequences that are available, bacterial classification remains a changing and expanding field. ^[4][115] For example, a few biologists argue that the Archaea and Eukaryotes evolved from Gram-positive bacteria. ^[116]

Identification of bacteria in the laboratory is particularly relevant in medicine, where the correct treatment is determined by the bacterial species causing an infection. Medicine is the art and science of healing It encompasses a range of Health care practices evolved to maintain and restore Human Health by the Consequently, the need to identify human pathogens was a major impetus for the development of techniques to identify bacteria.

The Gram stain, developed in 1884 by Hans Christian Gram, characterises bacteria based on the structural characteristics of their cell walls. Gram staining (or Gram's method) is an empirical method of differentiating bacterial species into two large groups ( Gram-positive and Hans Christian Joachim Gram ( September 13, 1853 - November 14, 1938) was a Danish Bacteriologist. ^[57] The thick layers of peptidoglycan in the "Gram-positive" cell wall stain purple, while the thin "Gram-negative" cell wall appears pink. By combining morphology and Gram-staining, most bacteria can be classified as belonging to one of four groups (Gram-positive cocci, Gram-positive bacilli, Gram-negative cocci and Gram-negative bacilli). Some organisms are best identified by stains other than the Gram stain, particularly mycobacteria or Nocardia, which show acid-fastness on Ziehl–Neelsen or similar stains. Acid-fastness is a physical property of some bacteria referring to their resistance to decolorization by acids during staining procedures The Ziehl-Neelsen stain, also known as the acid-fast stain, was first described by two German doctors Franz Ziehl (1859 to 1926 a bacteriologist and Friedrich ^[118] Other organisms may need to be identified by their growth in special media, or by other techniques, such as serology. Serology is the scientific study of blood serum. In practice the term usually refers to the Diagnostic identification of antibodies in the serum

Culture techniques are designed to promote the growth and identify particular bacteria, while restricting the growth of the other bacteria in the sample. A microbiological culture, AKA microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory Often these techniques are designed for specific specimens; for example, a sputum sample will be treated to identify organisms that cause pneumonia, while stool specimens are cultured on selective media to identify organisms that cause diarrhoea, while preventing growth of non-pathogenic bacteria. Sputum is matter that is Expectorated from the respiratory tract such as Mucus or Phlegm, mixed with Saliva, which can then be spat Pneumonia is an inflammatory illness of the Lung. Frequently it is described as lung Parenchyma / alveolar inflammation and abnormal Feces, faeces, or fæces (see spelling differences) is a waste product from an animal's digestive tract expelled through the Anus A growth medium or culture medium is a liquid or gel designed to support the growth of Microorganisms or cells There are different types of media for In Medicine, diarrhea, also spelled diarrhoea (see spelling differences) is frequent loose or liquid Bowel movements Acute diarrhea Specimens that are normally sterile, such as blood, urine or spinal fluid, are cultured under conditions designed to grow all possible organisms. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells ��such as nutrients and oxygen—and transports Waste products Urine is a liquid waste product of the body secreted by the Kidneys by a process of filtration from Blood and Excreted through the Urethra. Cerebrospinal fluid ( CSF) Liquor cerebrospinalis, is a clear Bodily fluid that occupies the Subarachnoid space and the Ventricular system ^[119][87] Once a pathogenic organism has been isolated, it can be further characterised by its morphology, growth patterns such as (aerobic or anaerobic growth, patterns of hemolysis) and staining. An aerobic organism or aerobe is an Organism that has an Oxygen based Metabolism. An anaerobic organism is any Organism that does not require Oxygen for growth and may even die in its presence Hemolysis is the breakdown of Red blood cells. The ability of bacterial colonies to induce hemolysis when grown on Blood agar is used to classify certain Microorganisms

As with bacterial classification, identification of bacteria is increasingly using molecular methods. Diagnostics using such DNA-based tools, such as polymerase chain reaction, are increasingly popular due to their specificity and speed, compared to culture-based methods. ^[120] These methods also allow the detection and identification of "viable but nonculturable" cells that are metabolically active but non-dividing. ^[121] However, even using these improved methods, the total number of bacterial species is not known and cannot even be estimated with any certainty. Attempts to quantify bacterial diversity have ranged from 10⁷ to 10⁹ total species, but even these diverse estimates may be out by many orders of magnitude. ^[122][123]

Interactions with other organisms

Despite their apparent simplicity, bacteria can form complex associations with other organisms. These symbiotic associations can be divided into parasitism, mutualism and commensalism. This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek Parasitism is a type of symbiotic relationship between Organisms of different Species. Mutualism is a Biological interaction between individuals of two different Species, where both individuals derive a fitness benefit for example increased In Ecology, commensalism is a kind of symbiotic relationship between two organisms where one benefits and the other is not significantly harmed or helped (like a bird Due to their small size, commensal bacteria are ubiquitous and grow on animals and plants exactly as they will grow on any other surface. However, their growth can be increased by warmth and sweat, and large populations of these organisms in humans are the cause of body odor. Body odor (spelled body odour outside the United States often abbreviated as B

Mutualists

Certain bacteria form close spatial associations that are essential for their survival. One such mutualistic association, called interspecies hydrogen transfer, occurs between clusters of anaerobic bacteria that consume organic acids such as butyric acid or propionic acid and produce hydrogen, and methanogenic Archaea that consume hydrogen. An anaerobic organism is any Organism that does not require Oxygen for growth and may even die in its presence Butyric acid (from Greek βούτυρος = butter) also known under the systematic name butanoic acid, is a Carboxylic acid with the structural Propionic acid (systematically named propanoic acid) is a naturally-occurring Carboxylic acid with Chemical formula C[[Hydrogen H]]3CH2C Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Methanogens are Archaea that produce Methane as a Metabolic byproduct in Anoxic conditions ^[124] The bacteria in this association are unable to consume the organic acids as this reaction produces hydrogen that accumulates in their surroundings. Only the intimate association with the hydrogen-consuming Archaea keeps the hydrogen concentration low enough to allow the bacteria to grow.

In soil, microorganisms which reside in the rhizosphere (a zone that includes the root surface and the soil that adheres to the root after gentle shaking) carry out nitrogen fixation, converting nitrogen gas to nitrogenous compounds. Rhizosphere is the narrow region of Soil that is directly influenced by Root secretions and associated soil Microorganisms ref> ROOT is an object-oriented program and library developed by CERN. Nitrogen fixation is the process by which Nitrogen is taken from its natural relatively inert molecular form (N2 in the atmosphere and converted into ^[125] This serves to provide an easily absorbable form of nitrogen for many plants, which cannot fix nitrogen themselves. Many other bacteria are found as symbionts in humans and other organisms. This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek The human flora is the Microrganisms that constantly inhabit the Human body. For example, the presence of over 1,000 bacterial species in the normal human gut flora of the intestines can contribute to gut immunity, synthesise vitamins such as folic acid, vitamin K and biotin, convert milk protein to lactic acid (see Lactobacillus), as well as fermenting complex undigestible carbohydrates. The gut flora are the Microorganisms that normally live in the Digestive tract and can perform a number of useful functions for their hosts In Anatomy, the intestine is the segment of the alimentary canal extending from the Stomach to the Anus and in humans and other mammals consists A vitamin is an Organic compound required as a Nutrient in tiny amounts by an Organism. Folic acid (also known as Vitamin M and Folacin) and Folate (the Anionic form are forms of the water-soluble Vitamin B9 Vitamin K (K from "Koagulations-Vitamin" in German Danish Swedish and Norwegian denotes a group of Lipophilic, Hydrophobic Vitamins that Vitamin H redirects here In medical slang "vitamin H" may also refer to Haloperidol. Milk is an opaque white liquid produced by the Mammary glands of female Mammals (including Monotremes. Lactic acid ( IUPAC Systematic name: 2-hydroxypropanoic acid) also known as milk acid, is a Chemical compound that plays a role Lactobacillus is a Genus of Gram-positive Facultative anaerobic or Microaerophilic Bacteria. Carbohydrates (from ' Hydrates of Carbon ' or saccharides ( Greek σάκχαρον meaning " Sugar " are the most ^{[126][127][128]} The presence of this gut flora also inhibits the growth of potentially pathogenic bacteria (usually through competitive exclusion) and these beneficial bacteria are consequently sold as probiotic dietary supplements. In Community ecology, the competitive exclusion principle, sometimes referred to as Gause's Law of competitive exclusion or just Gause's Law Probiotics are Dietary supplements containing potentially beneficial Bacteria or Yeasts According to the currently adopted definition by FAO / ^[129]

Pathogens

Main article: Pathogenic bacteria

If bacteria form a parasitic association with other organisms, they are classed as pathogens. Pathogenic bacteria are Bacteria that cause Infectious diseases. Salmonella enterica is a rod shaped Flagellated Gram-negative Bacterium, and a member of the Genus Salmonella A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious Pathogenic bacteria are a major cause of human death and disease and cause infections such as tetanus, typhoid fever, diphtheria, syphilis, cholera, foodborne illness, leprosy and tuberculosis. Tetanus is a medical condition that is characterized by a prolonged contraction of Skeletal muscle fibres Typhoid fever, also known as enteric fever, bilious fever, Yellow Jack or commonly just typhoid, is an illness caused by the Bacterium Diphtheria ( Greek διφθερα ( diphthera)—“pair of leather scrolls" is an upper respiratory tract illness characterized by sore Syphilis is a Sexually transmitted disease caused by the spirochetal Bacterium Treponema pallidum pallidum. Cholera, sometimes known as Asiatic cholera or epidemic cholera, is an infectious Gastroenteritis caused by the Bacterium Foodborne illness (also foodborne disease) is any Illness resulting from the consumption of food Leprosy (from the Greek lepi (λέπι meaning scales on a fish or Hansen's disease, is a chronic disease caused by the bacterium Tuberculosis (abbreviated as TB for tubercle bacillus or T u' b' erculosis Bacillus --> is a common A pathogenic cause for a known medical disease may only be discovered many years after, as was the case with Helicobacter pylori and peptic ulcer disease. Helicobacter pylori ( is a Gram-negative, microaerophilic Bacterium that inhabits various areas of the stomach and Duodenum. Wikipedia talkFeatured lists for an explanation of this and other inclusion tags below -->This is a timeline of the events relating to the discovery that peptic Bacterial diseases are also important in agriculture, with bacteria causing leaf spot, fire blight and wilts in plants, as well as Johne's disease, mastitis, salmonella and anthrax in farm animals. Agriculture refers to the production of goods through the growing of plants and fungi and the raising of domesticated Animals The study of agriculture Leaf Spots are round blemishes found on the leaves of many species of Plants mostly caused by Parasitic Fungi or Bacteria. Fireblight is a Contagious disease affecting Apples Pears and some other members of the family Rosaceae. Wilting refers to the loss of rigidity of non-woody parts of Plants This occurs when the Turgor pressure in non- lignified plant cells falls towards Johne's disease (pronounced "yo-knees" is a contagious chronic and sometimes fatal Infection that affects primarily the Small intestine of Ruminants Mastitis is the Inflammation of the Parenchyma of the Mammary gland ( Breast in Primates Udder in other mammals Salmonella is a Genus of rod-shaped Gram-negative enterobacteria that causes Typhoid fever, Paratyphoid fever Anthrax is an acute Disease in humans and animals caused by the bacterium Bacillus anthracis which is highly lethal in some forms

Each species of pathogen has a characteristic spectrum of interactions with its human hosts. In Biology, a host is an organism that harbors a Virus or Parasite, or a mutual or Commensal Symbiont, typically providing nourishment Some organisms, such as Staphylococcus or Streptococcus, can cause skin infections, pneumonia, meningitis and even overwhelming sepsis, a systemic inflammatory response producing shock, massive vasodilation and death. Staphylococcus (in Greek σταφυλη staphyle means bunch of grapes and κοκκος coccos means granule is a genus of Gram-positive Streptococcus is a Genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the Pneumonia is an inflammatory illness of the Lung. Frequently it is described as lung Parenchyma / alveolar inflammation and abnormal Meningitis is Inflammation of the protective membranes covering the Brain and Spinal cord, known collectively as the Meninges. Sepsis is a serious medical condition characterized by a whole-body inflammatory state (called a Systemic inflammatory response syndrome or SIRS caused ^[130] Yet these organisms are also part of the normal human flora and usually exist on the skin or in the nose without causing any disease at all. Anatomically a nose is a protuberance in Vertebrates that houses the Nostrils or nares which admit and expel air for respiration in conjunction with the Other organisms invariably cause disease in humans, such as the Rickettsia, which are obligate intracellular parasites able to grow and reproduce only within the cells of other organisms. Rickettsia is a Genus of motile, Gram-negative, non-sporeforming, highly Pleomorphic bacteria that can present One species of Rickettsia causes typhus, while another causes Rocky Mountain spotted fever. Typhus is any of several similar diseases caused by Louse -borne bacteria Rocky Mountain spotted fever is the most severe and most frequently reported Rickettsial illness in the United States. Chlamydia, another phylum of obligate intracellular parasites, contains species that can cause pneumonia, or urinary tract infection and may be involved in coronary heart disease. Chlamydia is a Genus of Bacteria in the family Chlamydiaceae, order Chlamydiales, class and phylum Chlamydiae A urinary tract infection ( UTI) is a bacterial Infection that affects any part of the Urinary tract. Coronary disease (or coronary heart disease) refers to the failure of Coronary circulation to supply adequate circulation to Cardiac muscle and surrounding ^[131] Finally, some species such as Pseudomonas aeruginosa, Burkholderia cenocepacia, and Mycobacterium avium are opportunistic pathogens and cause disease mainly in people suffering from immunosuppression or cystic fibrosis. Pseudomonas aeruginosa is a Gram-negative, aerobic, rod-shaped Bacterium with unipolar motility. Burkholderia cenocepacia is a Gram-negative bacteria that is common in the environment and may cause disease in plants Mycobacterium avium complex (MAC is a group of Genetically -related Bacteria belonging to the genus Mycobacterium. An opportunistic infection is an infection caused by Pathogens that usually do not cause disease in a healthy Immune system. Immunosuppression involves an act that reduces the activation or Efficacy of the Immune system. Cystic fibrosis (also known as CF, mucoviscoidosis, or mucoviscidosis) is a hereditary disease affecting the exocrine (mucus glands of the lungs ^[132][133]

Bacterial infections may be treated with antibiotics, which are classified as bacteriocidal if they kill bacteria, or bacteriostatic if they just prevent bacterial growth. In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa A bactericide or bacteriocide is a substance that kills bacteria and preferably nothing else Bacteriostatic Antibiotics limit the growth of bacteria by interfering with bacterial Protein production DNA replication or other aspects of There are many types of antibiotics and each class inhibits a process that is different in the pathogen from that found in the host. Enzyme inhibitors are Molecules that bind to Enzymes and decrease their activity. An example of how antibiotics produce selective toxicity are chloramphenicol and puromycin, which inhibit the bacterial ribosome, but not the structurally different eukaryotic ribosome. Chloramphenicol is a Bacteriostatic Antimicrobial originally derived from the Bacterium Streptomyces venezuelae, isolated by Puromycin is an Antibiotic that is a potent inhibitor of translation. Ribosomes ( from ribo nucleic acid and "Greek soma ( meaning body") are complexes of RNA and Protein that ^[134] Antibiotics are used both in treating human disease and in intensive farming to promote animal growth, where they may be contributing to the rapid development of antibiotic resistance in bacterial populations. Intensive farming or intensive agriculture is an Agricultural production system characterized by the high Inputs of Capital, Fertilizers Antibiotic resistance is the ability of a Microorganism to withstand the effects of Antibiotics. ^[135] Infections can be prevented by antiseptic measures such as sterilizating the skin prior to piercing it with the needle of a syringe, and by proper care of indwelling catheters. Antiseptics (from Greek αντί - anti, '"against" + σηπτικός - septikos, "putrefactive" are antimicrobial Surgical and dental instruments are also sterilized to prevent contamination and infection by bacteria. Sterilization (or sterilisation, see spelling differences) refers to any process that effectively kills or eliminates transmissible agents (such as Fungi Disinfectants such as bleach are used to kill bacteria or other pathogens on surfaces to prevent contamination and further reduce the risk of infection. Disinfectants are Antimicrobial agents that are applied to non-living objects to destroy Microorganisms, the process of which is known as disinfection. A bleach is a Chemical that removes color or whitens often via Oxidation.

Significance in technology and industry

Further information: Economic importance of bacteria

Bacteria, often Lactobacillus in combination with yeasts and molds, have been used for thousands of years in the preparation of fermented foods such as cheese, pickles, soy sauce, sauerkraut, vinegar, wine and yoghurt. The economic importance of bacteria derives from the fact that bacteria are exploited by humans in a number of beneficial ways Lactobacillus is a Genus of Gram-positive Facultative anaerobic or Microaerophilic Bacteria. Yeasts are a growth form of eukaryotic Microorganisms classified in the kingdom Fungi, with about 1500 Species currently described WikipediaManual_of_Style#National_varieties_of_English --> Molds (or Fermentation in Food processing typically refers to the conversion of Sugar to Alcohol using Yeast under Anaerobic conditions Cheese is a Food made from Milk, usually the milk of cows, Buffalo, Goats or sheep, by coagulation. Pickling, also known as brining or corning, is the process of preserving Food by Anaerobic fermentation in Brine (a solution Soy sauce ( US) soya sauce ( Commonwealth) shoyu ( Japan) or sillao ( Peru) is a fermented Sauce Sauerkraut ( English:, German:, Yiddish: ˈzɔi̯əʀˌkʀɔi̯t is finely shredded Cabbage that has been fermented by various Vinegar is an acidic liquid processed from the Fermentation of Ethanol in a process that yields its key ingredient Acetic acid (also called ethanoic acid Wine is an Alcoholic beverage made from the fermentation of Grape juice Yoghurt, yogurt, yoghourt, youghurt or yogourt (see spelling below is a ^[136][137]

The ability of bacteria to degrade a variety of organic compounds is remarkable and has been used in waste processing and bioremediation. Bioremediation can be defined as any process that uses Microorganisms Fungi, green plants or their Enzymes to return the natural environment altered Bacteria capable of digesting the hydrocarbons in petroleum are often used to clean up oil spills. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Petroleum ( L petroleum, from Greek πετρέλαιον, lit For the fictional character see Oil Slick (Transformers. An oil spill is the release of a Liquid Petroleum Hydrocarbon into ^[138] Fertilizer was added to some of the beaches in Prince William Sound in an attempt to promote the growth of these naturally occurring bacteria after the infamous 1989 Exxon Valdez oil spill. Prince William Sound is a sound of the Gulf of Alaska on the south coast of the U The Exxon Valdez oil spill occurred in Prince William Sound, Alaska, on March 24 1989 These efforts were effective on beaches that were not too thickly covered in oil. Bacteria are also used for the bioremediation of industrial toxic wastes. Bioremediation can be defined as any process that uses Microorganisms Fungi, green plants or their Enzymes to return the natural environment altered Toxic waste is waste material often in chemical form that can cause death or injury to living creatures ^[139] In the chemical industry, bacteria are most important in the production of enantiomerically pure chemicals for use as pharmaceuticals or agrichemicals. In Chemistry, an enantiomer ( from the Greek ἐνάντιος opposite and μέρος part or portion is one of two Stereoisomers that are nonsuperimposable Agrichemical (or agrochemical) a contraction of agricultural chemical, is a generic term for the various Chemical products used in ^[140]

Bacteria can also be used in the place of pesticides in the biological pest control. A pesticide is a substance or mixture of substances used to kill a pest. Biological control of pests in Agriculture is a method of controlling pests (including Insects Mites Weeds and plant diseases This commonly involves Bacillus thuringiensis (also called BT), a Gram-positive, soil dwelling bacterium. Bacillus thuringiensis is a Gram-positive, soil dwelling Bacterium of the Genus Bacillus. Subspecies of this bacteria are used as a Lepidopteran-specific insecticides under trade names such as Dipel and Thuricide. Lepidoptera is an order of Insect that includes Moths and butterflies. An insecticide is a Pesticide used against Insects in all developmental forms ^[141] Because of their specificity, these pesticides are regarded as environmentally friendly, with little or no effect on humans, wildlife, pollinators and most other beneficial insects. Environmental friendly, eco-friendly, and nature friendly are synonyms used to refer to Goods and services considered to inflict minimal harm Wildlife includes all non-domesticated plants animals and other organisms A pollinator is the biotic agent ( vector) that moves Pollen from the male Anthers of a Flower to the female stigma of a flower to accomplish Beneficial insects are any of a number of species of insects that perform valued services like Pollination and pest control ^[142][143]

Because of their ability to quickly grow and the relative ease with which they can be manipulated, bacteria are the workhorses for the fields of molecular biology, genetics and biochemistry. Molecular biology is the study of Biology at a molecular level Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as By making mutations in bacterial DNA and examining the resulting phenotypes, scientists can determine the function of genes, enzymes and metabolic pathways in bacteria, then apply this knowledge to more complex organisms. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins In Biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. ^[144] This aim of understanding the biochemistry of a cell reaches its most complex expression in the synthesis of huge amounts of enzyme kinetic and gene expression data into mathematical models of entire organisms. Enzyme kinetics is the study of the Chemical reactions that are catalysed by Enzymes, with a focus on their Reaction rates The study of Gene expression is the process by which inheritable information from a Gene, such as the DNA sequence, is made into a functional Gene product, such This is achievable in some well-studied bacteria, with models of Escherichia coli metabolism now being produced and tested. ^[145][146] This understanding of bacterial metabolism and genetics allows the use of biotechnology to bioengineer bacteria for the production of therapeutic proteins, such as insulin, growth factors, or antibodies. Biotechnology is Technology based on Biology, especially when used in Agriculture, Food science, and Medicine. Bioengineering (also known as Biological Engineering is the application of Engineering principles to address challenges in the fields of Biology and Medicine Insulin is a Hormone with intensive effects on both metabolism and several other body systems (eg vascular compliance The term growth factor refers to a naturally occurring Protein capable of stimulating cellular growth proliferation and Cellular differentiation. Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily ^[147][148]

See also

• Human flora
• Bioaerosol
• Biotechnology
• Contamination control
• Denitrification
• Desulforudis audaxviator
• Extremophiles
• Transgenic bacteria
• Microorganism

References

Further reading

• Alcamo IE (2001). Fundamentals of microbiology. Boston: Jones and Bartlett. ISBN 0-7637-1067-9.  
• Atlas RM (1995). Principles of microbiology. St. Louis: Mosby. ISBN 0-8016-7790-4.  
• Martinko JM, Madigan MT (2005). Brock Biology of Microorganisms, 11th ed. , Englewood Cliffs, N. J: Prentice Hall. ISBN 0-13-144329-1.  
• Holt JC, Bergey DH (1994). Bergey's manual of determinative bacteriology, 9th ed. , Baltimore: Williams & Wilkins. ISBN 0-683-00603-7.  
• Hugenholtz P, Goebel BM, Pace NR (1998). "Impact of culture-independent studies on the emerging phylogenetic view of bacterial diversity". J Bacteriol 180 (18): 4765–74. PMID 9733676.  
• Funke BR, Tortora GJ, Case CL (2004). Microbiology: an introduction, 8th ed,, San Francisco: Benjamin Cummings. ISBN 0-8053-7614-3.  

External links

• Bacterial Nomenclature Up-To-Date from DSMZ
• The largest bacteria
• Tree of Life: Eubacteria
• Videos of bacteria swimming and tumbling, use of optical tweezers and other videos.
• Planet of the Bacteria by Stephen Jay Gould
• On-line text book on bacteriology
• Animated guide to bacterial cell structure.

Stephen Jay Gould (September 10 1941 &ndash May 20 2002 was a prominent American paleontologist, evolutionary biologist, and historian of science

---

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic