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Mycobacterium
TEM micrograph of M. tuberculosis.
TEM micrograph of M. A micrograph, microphotograph or photomicrograph is a Photograph or similar image taken through a Microscope or similar device to show tuberculosis.
Scientific classification
Kingdom: Bacteria
Phylum: Actinobacteria
Order: Actinomycetales
Suborder: Corynebacterineae
Family: Mycobacteriaceae
Genus: Mycobacterium
Lehmann & Neumann 1896
Species

See below. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Actinobacteria or actinomycetes are a group of Gram-positive bacteria with high G+C ratio. Actinomycetales is an order of Actinobacteria. They are very diverse and contain a variety of subdivisions as well as yet unclassified isolates Corynebacterineae is a suborder of the Actinomycetales, and includes most of the Acid-fast bacteria In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank.

Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic Actinobacteria or actinomycetes are a group of Gram-positive bacteria with high G+C ratio. The genus includes pathogens known to cause serious diseases in mammals, including tuberculosis and leprosy. A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious Tuberculosis (abbreviated as TB for tubercle bacillus or T u' b' erculosis Bacillus --> is a common Leprosy (from the Greek lepi (λέπι meaning scales on a fish or Hansen's disease, is a chronic disease caused by the bacterium [1] The Latin prefix "myco—" means both fungus and wax; its use here relates to the "waxy" compounds in the cell wall. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome.

Contents

Microbiologic characteristics

Mycobacterial cell wall: 1-outer lipids, 2-mycolic acid, 3-polysaccharides (arabinogalactan), 4-peptidoglycan, 5-plasma membrane, 6-lipoarabinomannan (LAM), 7-phosphatidylinositol mannoside, 8-cell wall skeleton
Mycobacterial cell wall: 1-outer lipids, 2-mycolic acid, 3-polysaccharides (arabinogalactan), 4-peptidoglycan, 5-plasma membrane, 6-lipoarabinomannan (LAM), 7-phosphatidylinositol mannoside, 8-cell wall skeleton

Mycobacteria are aerobic and nonmotile bacteria (except for the species Mycobacterium marinum which has been shown to be motile within macrophages) that are characteristically acid-alcohol fast. Mycobacterium is a Genus of Actinobacteria, given its own family the Mycobacteriaceae 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 Mycolic acids are long Fatty acids found in the Cell walls of the mycolata Taxon, a group of Bacteria that includes Mycobacterium Polysaccharides are relatively complex Carbohydrates They are Polymers made up of many Monosaccharides joined together by Glycosidic bonds Not to be confused with Glycoprotein. Peptidoglycan, also known as murein, is a Polymer consisting of sugars and amino The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer Lipoarabinomannan, also called LAM, is a Glycolipid, and a Virulence factor associated with Mycobacterium tuberculosis, the Bacteria History Mycobacterium marinum (formerly M balnei) is a Free-living bacterium, which causes Opportunistic infections in humans Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that Acid-fastness is a physical property of some bacteria referring to their resistance to decolorization by acids during staining procedures [1] Mycobacteria do not contain endospores or capsules, and are usually considered Gram-positive. An endospore is a dormant, tough and non-reproductive structure produced by a small number of Bacteria from the Firmicute phylum Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. While mycobacteria do not seem to fit the Gram-positive category from an empirical standpoint (i. A central concept in Science and the Scientific method is that all Evidence must be empirical, or empirically based that is dependent on evidence e. they do not retain the crystal violet stain), they are classified as an acid-fast Gram-positive bacterium due to their lack of an outer cell membrane. The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer All Mycobacterium species share a characteristic cell wall, thicker than in many other bacteria, which is hydrophobic, waxy, and rich in mycolic acids/mycolates. 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 In Chemistry, hydrophobicity (from the combining form of water in Attic Greek hydro- and for fear phobos) refers to the physical property of Mycolic acids are long Fatty acids found in the Cell walls of the mycolata Taxon, a group of Bacteria that includes Mycobacterium The cell wall makes a substantial contribution to the hardiness of this genus.

Many Mycobacterium species adapt readily to growth on very simple substrates, using ammonia or amino acids as nitrogen sources and glycerol as a carbon source in the presence of mineral salts. In Biology a substrate is the surface a plant or animal lives upon Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Optimum growth temperatures vary widely according to the species and range from 25 °C to over 50 °C.

Some species can be very difficult to culture (i. A microbiological culture, AKA microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory e. they are fastidious), sometimes taking over two years to develop in culture. Further, some species also have extremely long reproductive cycles — M. leprae, may take more than 20 days to proceed through one division cycle (for comparison, some E. coli strains take only 20 minutes), making laboratory culture a slow process. Mycobacterium leprae, also known as Hansen’s bacillus, mostly found in warm tropical countries is the Bacterium that causes Leprosy (Hansen's [1]

A natural division occurs between slowly– and rapidly–growing species. Mycobacteria that form colonies clearly visible to the naked eye in more than 7 days on subculture are termed slow growers Mycobacteria that form colonies clearly visible to the naked eye in less than 7 days on subculture are termed rapid growers Mycobacteria that form colonies clearly visible to the naked eye within 7 days on subculture are termed rapid growers, while those requiring longer periods are termed slow growers. Mycobacteria are slightly curved or straight rods between 0. 2-0. 6 µm wide by 1. 0-10 µm long.

Pigmentation

Some mycobacteria produce carotenoid pigments without light. Carotenoids are organic Pigments that are naturally occurring in Chromoplasts of plants and some other photosynthetic Organisms Others require photoactivation for pigment production.

Staining characteristics

Mycobacteria are classical acid-fast organisms. Acid-fastness is a physical property of some bacteria referring to their resistance to decolorization by acids during staining procedures [2] Stains used in evaluation of tissue specimens or microbiological specimens include Fite's stain, Ziehl-Neelsen stain, and Kinyoun stain. 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

Mycobacteria appear phenotypically most closely related to members of Nocardia, Rhodococcus and Corynebacterium. Nocardia is a Genus of Gram-positive, catalase-positive, rod-shaped Bacteria. Rhodococcus is a genus of aerobic non-sporulating non-motile Gram-positive bacteria closely related to Mycobacteria and Corynebacteria. Corynebacterium is a Genus of Gram-positive,aerobic or facultatively anaerobic, non- Motile, non-sporulated rod-shaped Actinobacteria

Ecological characteristics

Mycobacteria are widespread organisms, typical living in water (including tap water treated with chlorine) and food sources. Tap water ( running water) is part of indoor Plumbing, which became available in the late 19th century and common in the mid-20th century Water purification is the process of removing contaminants and other harmful microorganisms from a raw water source Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Some, however, including the tuberculosis and the leprosy organisms, appear to be obligate parasites and are not found as free-living members of the genus. An obligate parasite is a parasitic Organism that cannot live independently of its host.

Pathogenicity

Mycobacteria can colonize their hosts without the hosts showing any adverse signs. For example, billions of people around the world are infected with M. tuberculosis but will never know it because they will not develop symptoms. Mycobacterium tuberculosis is the Bacterium that causes most cases of Tuberculosis.

Mycobacterial infections are notoriously difficult to treat. The organisms are hardy due to their cell wall, which is neither truly Gram negative nor positive, and unique to the family, they are naturally resistant to a number of antibiotics that work by destroying cell walls, such as penicillin. Gram-negative bacteria are those Bacteria that do not retain Crystal violet dye in the Gram staining protocol Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa Penicillin (sometimes abbreviated PCN or pen) is a group of Beta-lactam antibiotics used in the treatment of Bacterial Infections Also, because of this cell wall, they can survive long exposure to acids, alkalis, detergents, oxidative bursts, lysis by complement and antibiotics which naturally leads to antibiotic resistance. The complement system is a Biochemical cascade that helps clear Pathogens from an organism 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. Most mycobacteria are susceptible to the antibiotics clarithromycin and rifamycin, but antibiotic-resistant strains are known to exist. Clarithromycin is a Macrolide Antibiotic used to treat Pharyngitis, Tonsillitis, acute maxillary Sinusitis, acute bacterial exacerbation The rifamycins are a group of Antibiotics which are synthesized either naturally by the bacterium Amycolatopsis mediterranei, or artificially

Medical classification

Mycobacteria can be classified into several major groups for purpose of diagnosis and treatment: M. tuberculosis complex which can cause tuberculosis: M. Tuberculosis (abbreviated as TB for tubercle bacillus or T u' b' erculosis Bacillus --> is a common tuberculosis, M. bovis, M. africanum, and M. microti; M. leprae which causes Hansen's disease or leprosy; Nontuberculous mycobacteria (NTM) are all the other mycobacteria which can cause pulmonary disease resembling tuberculosis, lymphadenitis, skin disease, or disseminated disease. Leprosy (from the Greek lepi (λέπι meaning scales on a fish or Hansen's disease, is a chronic disease caused by the bacterium Nontuberculous mycobacteria (NTM also known as environmental mycobacteria, atypical mycobacteria and mycobacteria other than tuberculosis (MOTT are

Phenotypic testing

Various phenotypic tests can be used to identify and distinguish different Mycobacteria species and strains.

Phenotypic testing of Mycobacteria

Mycosides

Mycosides are phenolic alcohols (such as phenolphthiocerol) that were shown to be components of mycobacterium glycolipids which are termed glycosides of phenolphthiocerol dimycocerosate (Smith DW et al. A variety of phenotypic tests can be used to identify and distinguish Mycobacteria strains and species from each other Glycolipids are Carbohydrate -attached Lipids. Their role is to provide Energy and also serve as markers for cellular recognition , Nature 1960, 186, 887) There are 18 and 20 carbon atoms in mycosides A, and B, respectively. [3]

Species

Databases on Mycobacterium tuberculosis

References

  1. ^ a b c Ryan KJ, Ray CG (editors) (2004). Mycobacterium africanum is a species of Mycobacterium that is most commonly found in West African countries Mycobacterium canetti, a novel pathogenic taxon of the Mycobacterium tuberculosis complex was described in 1997 by D van Soolingen et al Mycobacterium caprae Type strain strain spc-1 = gM-1 = ATCC BAA-824 = CIP 105776 Mycobacterium pinnipedii is a member of the Mycobacterium tuberculosis complex which primarily infects seals Mycobacterium tusciae is a slow-growing scotochromogenic Mycobacterium first isolated from a lymph node of an immunocompromised child and subsequently from tap Mycobacterium ulcerans ( M Ulcerans) is a slow-growing Mycobacterium that classically infects the Skin and Subcutaneous tissues The Buruli ulcer (also known as the Bairnsdale ulcer) is an Infectious disease caused by Mycobacterium ulcerans. Mycobacterium vaccae is a non-pathogenic species of the Mycobacteriaceae family of bacteria that lives naturally in Soil. Mycobacterium vanbaalenii is a rapidly growing Mycobacterium that can utilize Polycyclic aromatic hydrocarbons. Mycobacterium wolinskyi is a rapidly growing Mycobacterium most commonly seen in post-traumatic wound infections especially those following open fractures and Mycobacterium xenopi is a slow-growing Scotochromogenic species of Mycobacterium. Sherris Medical Microbiology, 4th ed. , McGraw Hill. ISBN 0-8385-8529-9.  
  2. ^ McMurray DN (1996). "Mycobacteria and Nocardia", in Baron S et al (eds. ): Baron's Medical Microbiology, 4th ed. , Univ of Texas Medical Branch. ISBN 0-9631172-1-1.  
  3. ^ fatty alcohols and aldehydes

Further reading

Dictionary

mycobacterium

-noun

  1. (biology) Any of many rod-shaped, aerobic bacteria, of the genus Mycobacterium, that cause diseases such as tuberculosis and leprosy
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