An endosymbiont is any organism that lives within the body or cells of another organism, i. e. forming an endosymbiosis (Greek: endo = inner, sym = together and biosis = living). Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Examples are nitrogen-fixing bacteria (called rhizobia) which live in root nodules on legume roots, single-celled algae inside reef-building corals, and bacterial endosymbionts that provide essential nutrients to about 10%–15% of insects. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Rhizobia (from the Greek words rhiza = root and bios = Life are Soil bacteria that fix Nitrogen ( Diazotrophy Root nodules occur on the roots of plants that associate with Vigna bacteria. A legume is a Plant in the family Fabaceae (or Leguminosae or a Fruit of these specific plants Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Corals are Marine organisms from the class Anthozoa and exist as small Sea anemone –like Polyps typically in colonies of many

Many instances of endosymbiosis are obligate, that is either the endosymbiont or the host cannot survive without the other, such as the gutless marine worms of the genus Riftia, which get nutrition from their endosymbiotic bacteria. Siboglinidae, also known as the beard worms, is a family of Polychaete annelid worms whose members made up the former phyla A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic Giant tube worms, Riftia pachyptila, are marine Invertebrates in the phylum Annelida ref> (formerly grouped in phylum Pogonophora However, not all endosymbioses are obligate. Also, some endosymbioses can be harmful to either of the organisms involved. See symbiosis for further discussion of this issue. This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek

It is generally agreed that certain organelles of the eukaryotic cell, especially mitochondria and plastids such as chloroplasts, originated as bacterial endosymbionts. 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 Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Plastids are major Organelles found in plants and algae Plastids often contain pigments used in photosynthesis and the types of pigments present can change Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. This theory is called the endosymbiotic theory, which was first articulated by the Russian botanist Konstantin Mereschkowski in 1905^[1]. The endosymbiotic theory concerns the origins of mitochondria and Plastids (e Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending Botany, plant science(s, phytology, or plant biology is a branch of Biology and is the scientific study of plant Life Konstantin Sergejewicz Mereschkowsky (1855-1921 ( Russian: Константин Сергеевич Мережковский also transliterated Konstantin Sergeevich Year 1905 ( MCMV) was a Common year starting on Sunday (link will display full calendar of the Gregorian calendar (or a Common year starting

Contents 1 The endosymbiont theory and mitochondria and chloroplasts 2 Bacterial endosymbionts in marine oligochaetes 3 Bacterial endosymbionts in other marine invertebrates 4 Symbiodinium dinoflagellate endosymbionts in marine metazoa and protists 5 Endosymbionts in protists 6 Bacterial obligate endosymbionts in insects 7 Viral endosymbionts, endogenous retrovirus (ERV) 8 Notes 9 References and external links 9.1 Obligate bacterial endosymbiosis in marine oligochaetes: 9.2 Bacterial endosymbionts in echinoderms: 9.3 Symbiodinium dinoflagellate endosymbionts in marine metazoa and protists 9.4 Obligate bacterial endosymbionts in insects: 10 See also

The endosymbiont theory and mitochondria and chloroplasts

Main article: Endosymbiotic theory

The endosymbiont theory attempts to explain the origins of organelles such as mitochondria and chloroplasts in eukaryotic cells. The endosymbiotic theory concerns the origins of mitochondria and Plastids (e The theory proposes that chloroplasts and mitochondria evolved from certain types of bacteria that prokaryotic cells engulfed through endophagocytosis. These cells and the bacteria trapped inside them entered a symbiotic relationship, a close association between different types of organisms over an extended time. However, more specifically, the relationship was endosymbiotic, meaning that one of the organisms (the bacteria) lived within the other (the prokaryotic cells).

According to this endosymbiont theory, an anaerobic cell probably ingested an aerobic bacterium but failed to digest on it. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have The aerobic bacterium flourished within the cell because the cell's cytoplasm was abundant in half-digested food molecules. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by The bacterium digested these molecules with oxygen and gained great amounts of energy. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Because the bacterium had so much energy, it probably leaked some of it as Adenosine triphosphate into the cell's cytoplasm. Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy This benefited the anaerobic cell because it enabled it to digest food aerobically. Eventually, the aerobic bacterium could no longer live independently from the cell, and it therefore became a mitochondrion. The origin of the chloroplast is very similar to that of the mitochondrion. A cell must have captured a photosynthetic cyanobacterium and failed to digest it. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. The cyanobacterium thrived in the cell and eventually evolved into the first chloroplast. Other eukaryotic organelles may have also evolved through endosymbiosis. Scientists believe that cilia, flagella, centrioles, and microtubules may have come from a symbiosis between a spirilla-like bacterium and an early eukaryotic cell. A cilium (plural cilia) is an Organelle found in eukaryotic cells Cilia are tail-like projections extending approximately A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it A Centriole is a barrel shaped Organelle found in most animal Eukaryotic cells though absent in Higher plants and Fungi. Microtubules are one of the components of the Cytoskeleton. They have a diameter of 25 nm and length varying from 200 nanometers to 25 micrometers

There are several examples of evidence that support the endosymbiont theory. Mitochondria and chloroplasts contain their own small supply of DNA, which may be remnants of the genome the organelles had when they were independent aerobic bacteria. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby The single most convincing evidence of the descent of organelles from bacteria is the position of mitochondria and plastid DNA sequences in phylogenetic trees of bacteria. A tree is a perennial Woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or Mitochondria have sequences that clearly indicate origin from a group of bacteria called the alpha-Proteobacteria. Plastids have DNA sequences that indicate origin from the cyanobacteria (blue-green algae). In addition, there are organisms alive today, called living intermediates, that are in a similar endosymbiotic condition to the prokaryotic cells and the aerobic bacteria. Living intermediates show that the evolution proposed by the endosymbiont theory is possible. For example, the giant amoeba Pelomyxa lacks mitochondria but has aerobic bacteria that carry out a similar role. Pelomyxa are giant amoebae usually 500-800 μm but occasionally up to 5 mm in length A variety of corals, clams, snails, and one species of Paramecium permanently host algae in their cells. Corals are Marine organisms from the class Anthozoa and exist as small Sea anemone –like Polyps typically in colonies of many Clam is a word which can be used for all some or only a few Species of Bivalve Mollusks the word is a Common name which has The word snail is a Common name that can be used for almost all members of the Molluscan class Gastropoda which have coiled shells in the Paramecia are a group of Unicellular Ciliate Protozoa formerly known as “slipper Animalcules �� from their Slipper shape are commonly Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Many of the insect endosymbionts have been shown to have ancient associations with their hosts, involving strictly vertical inheritance. "Heir" and "Heiress" redirect here For the men and women fragrances endorsed by Paris Hilton see Heiress (fragrance. In addition, these insect symbionts have similar patterns of genome evolution to those found in true organelles: genome reduction, rapid rates of gene evolution, and bias in nucleotide base composition favoring adenine and thymine, at the expense of guanine and cytosine. eVolution is the third Album by eLDee, it was due to be released in 2008 Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group Adenine is a Purine with a variety of roles in Biochemistry including Cellular respiration, in the form of both the energy-rich Adenosine Thymine is one of the four bases in the Nucleic acid of DNA that make up the letters ATGC 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

Further evidence of endosymbiosis are the prokaryotic ribosomes found within chloroplasts and mitochondria as well as the double membrane enclosing them. The inner membrane is thought to be the original membrane of the once independent prokaryote, while the outer one is thought to be the food vacuole it was enclosed in initially. Triple or quadruple membranes are found among certain algae, probably resulting from repeated endosymbiosis (although little else was retained of the engulfed cell).

These modern organisms with endosymbiotic relationships with aerobic bacteria have verified the endosymbiotic theory, which explains the origin of mitochondria and chloroplasts from bacteria. Researchers in molecular and evolutionary biology no longer question this theory, although some of the details, such as the mechanisms for loss of genes from organelles to host nuclear genomes, are still being worked out. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance

Bacterial endosymbionts in marine oligochaetes

Some marine oligochaeta (e. For the plant Genus from the sunflower family ( Asteraceae) see Oligochaeta (plant. g Olavius or Inanidrillus) have obligate extracellular endosymbionts that fill the entire body of their host. These marine worms are nutritionally dependent on their symbiotic chemoautotrophic bacteria lacking any digestive or excretory system (no gut, mouth or nephridia). Chemotrophs are organisms that obtain Energy by the Oxidation of Electron donating Molecules in their environments Nephridia are invertebrate organs which function similarly to Kidneys They remove Metabolic wastes from an animal's body

Bacterial endosymbionts in other marine invertebrates

Extracellular endosymbionts are also represented in all 5 extant classes of Echinodermata (Crinoidea, Ophiuroidea, Asteroidea, Echinoidea, and Holothuroidea). Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) Crinoids, also known as sea lilies or feather-stars, are marine animals that make up the class Crinoidea of the Echinoderms (phylum Echinodermata Brittle stars, or ophiurids, are Echinoderms closely related to Sea stars. Starfish (also called sea stars) are any Echinoderms belonging to the class Asteroidea. Sea urchins are small globular spiny sea cat animals composing most of class Echinoidea. The sea cucumber (also known as trepang, bêche-de-mer, or ambiguously Sea slug) is an Echinoderm of the class Holothuroidea Little is known of the nature of the association (mode of infection, transmission, metabolic requirements, etc. ) but phylogenetic analysis indicates that these symbionts belong to the alpha group of the class Proteobacteria, relating them to Rhizobium and Thiobacillus. The Proteobacteria are a major group ( Phylum) of Bacteria. They include a wide variety of Pathogens such as Escherichia, Other studies indicate that these subcuticular bacteria may be both abundant within their hosts and widely distributed among the Echinoderms in general.

Symbiodinium dinoflagellate endosymbionts in marine metazoa and protists

Dinoflagellate endosymbionts of the genus Symbiodinium, commonly known as zooxanthellae, are found in corals, mollusks (esp. The dinoflagellates are a large group of Flagellate Protists Most are marine Plankton, but Zooxanthellae (plural ˌzoʊoʊzænˈθɛli are golden-brown intracellular Endosymbionts of various marine Animals and Protozoa, especially Anthozoans Corals are Marine organisms from the class Anthozoa and exist as small Sea anemone –like Polyps typically in colonies of many Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 giant clams, the Tridacna), sponges, and foraminifera. In Japanese cuisine, Geoduck (mirugai is sometimes referred to as "giant clam" The sponges or poriferans (from Latin porus "pore" and ferre "to bear" are Animals The Foraminifera, ("Hole Bearers" or forams for short are a large group of Amoeboid Protists with reticulating Pseudopods fine These endosymbionts drive the amazing formation of coral reefs by capturing sunlight and providing their hosts with energy for carbonate deposition. Coral reefs are Aragonite structures produced by living organisms found in marine waters with little to no nutrients in the water In Chemistry, a carbonate is a salt or Ester of Carbonic acid.

Previously thought to be a single species, molecular phylogenetic evidence over the past couple decades has shown there to be great diversity in Symbiodinium. In some cases there is specificity between host and Symbiodinium clade. More often, however, there is an ecological distribution of Symbiodinium, the symbionts switching between hosts with apparent ease. When reefs become environmentally stressed, this distribution of symbionts is related to the observed pattern of coral bleaching and recovery. Coral bleaching is the loss of color of Corals due to stress-induced expulsion of symbiotic Unicellular Algae or due to the loss of pigmentation within Thus the distribution of Symbiodinium on coral reefs and its role in coral bleaching presents one of the most complex and interesting current problems in reef ecology. Ecology (from Greek grc οἶκος oikos, "house(hold" and grc -λογία -logia) is the scientific study of

Endosymbionts in protists

Mixotricha paradoxa is a protozoan that lacks mitochondria, however, spherical bacteria live inside the cell and serve the function of the mitochondria. Mixotricha paradoxa is a species of Protozoan that lives inside the Termite species Mastotermes darwiniensis and has multiple Mixotricha also has three other species of symbionts that live on the surface of the cell.

Paramecium bursaria, a species of ciliate, has a mutualistic symbiotic relationship with green alga called Zoochlorella. Paramecium bursaria is a species of Ciliate Protozoan that has a mutualistic symbiotic relationship with green Alga called The ciliates are one of the most important groups of Protists common almost everywhere there is water — lakes ponds oceans rivers and soils with many ectosymbiotic The algae live inside the cell, in the cytoplasm.

Bacterial obligate endosymbionts in insects

Scientists classify insect endosymbionts in two broad categories, 'Primary' and 'Secondary'. Primary endosymbionts (sometimes referred to as P-endosymbionts) have been associated with their insect hosts for many millions of years (from 10 to several hundred million years in some cases), they form obligate associations (see below), and display cospeciation with their insect hosts. Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described Secondary endosymbionts exhibit a more recently developed association, are sometimes horizontally transferred between hosts, live in the haemolymph of the insects (not specialized bacteriocytes, see below), and are not obligate. Hemolymph or haemolymph is the Blood analogue used by all Arthropods and most Mollusks that have an Open circulatory system.

Among primary endosymbionts of insects, the best studied are the pea aphid (Acyrthosiphon pisum) and its endosymbiont Buchnera sp. Buchnera aphidicola a member of the Proteobacteria, is the primary endosymbiont of Aphids (A APS^[2], the tsetse fly Glossina morsitans morsitans and its endosymbiont Wigglesworthia glossinidia brevipalpis and the endosymbiotic protists in lower termites. This page is about the insect For other meanings see Tsetse (disambiguation. Wigglesworthia glossinidia brevipalpis is a Gram-negative Bacterium in the family Enterobacteriaceae, related to E Protists (ˈproʊtɨst are a diverse group of eukaryotic Microorganisms Historically protists were treated as the kingdom Protista but this The termites are a group of Social Insects usually classified at the taxonomic rank of order Isoptera (but see also taxonomy As with endosymbiosis in other insects, the symbiosis is obligate in that neither the bacteria nor the insect is viable without the other. Scientists have been unable to cultivate the bacteria in lab conditions outside of the insect. With special nutritionally-enhanced diets, the insects can survive, but are unhealthy, and at best survive only a few generations.

In some insect groups, these endosymbionts live in specialized insect cells called bacteriocytes (also called mycetocytes), and are maternally-transmitted, i. A bacteriocyte ( Greek for bacteria cell) also called a mycetocyte, is a specialized Adipocyte found in some Insect groups such as e. the mother transmits her endosymbionts to her offspring. In some cases, the bacteria are transmitted in the egg, as in Buchnera; in others like Wigglesworthia, they are transmitted via milk to the developing insect embryo. Milk is an opaque white liquid produced by the Mammary glands of female Mammals (including Monotremes. In termites, the endosymbionts reside within the hindguts and are transmitted through trophallaxis among colony members. Trophallaxis is the transfer of food or other fluids among members of a Community through mouth-to-mouth ( stomodeal) or anus-to-mouth ( proctodeal) feeding

The primary endosymbionts are thought to help the host either by providing nutrients that the host cannot obtain itself, or by metabolizing insect waste products into safer forms. For example, the putative primary role of Buchnera is to synthesize essential amino acids that the aphid cannot acquire from its natural diet of plant sap. An essential amino acid or indispensable amino acid is an Amino acid that cannot be synthesized de novo by the organism (usually referring to Similarly, the primary role of Wigglesworthia is probably to synthesize vitamins that the tsetse fly does not get from the blood that it eats. A vitamin is an Organic compound required as a Nutrient in tiny amounts by an Organism. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells ��such as nutrients and oxygen—and transports Waste products In lower termites, the endosymbiotic protists play a major role in the digestion of lignocellulosic materials which constitutes a bulk of the termites' diet.

Bacteria benefit from the reduced exposure to predators, the ample supply of nutrients and relative environmental stability inside the host.

Genome sequencing reveals that obligate bacterial endosymbionts of insects have among the smallest of known bacterial genomes and have lost many genes that are commonly found in closely related bacteria. Genome size refers to the total amount of DNA contained within one copy of a Genome. Several theories have been put forth to explain the loss of genes. Presumably some of these genes are not needed in the environment of the host insect cell. A complementary theory suggests that the relatively small numbers of bacteria inside each insect decrease the efficiency of natural selection in 'purging' deleterious mutations and small mutations from the population, resulting in a loss of genes over many millions of years. Research in which a parallel phylogeny of bacteria and insects was inferred supports the belief that the primary endosymbionts are transferred only vertically (i. e. from the mother), and not horizontally (i. e. by escaping the host and entering a new host).

Attacking obligate bacterial endosymbionts may present a way to control their insect hosts, many of which are pests or carriers of human disease. For example aphids are crop pests and the tsetse fly carries the organism Trypanosoma brucei that causes African sleeping sickness. Trypanosoma brucei is a parasitic Protist species that causes African trypanosomiasis (or Sleeping sickness) in humans and Nagana Sleeping sickness or human African trypanosomiasis is a Parasitic Disease of people and animals caused by Protozoa of species Other motivations for their study is to understand symbiosis, and to understand how bacteria with severely depleted genomes are able to survive, thus improving our knowledge of genetics and molecular biology. Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Molecular biology is the study of Biology at a molecular level

Less is known about secondary endosymbionts. The pea aphid (Acyrthosiphon pisum) is known to contain at least three secondary endosymbionts, Hamiltonella defensa, Regiella insecticola, and Serratia symbiotica. H. defensa aids in defending the insect from parasitoids. Sodalis glossinidius is a secondary endosymbiont tsetse flies that lives inter- and intracellularly in various host tissues, including the midgut and hemolymph. Phylogenetic studies have not indicated a correlation between evolution of Sodalis and tsetse. ^[3] Unlike tsetse's P-symbiont Wigglesworthia, though, Sodalis has been cultured in vitro. ^[4]

Viral endosymbionts, endogenous retrovirus (ERV)

Main article: Endogenous retrovirus

During pregnancy in viviparous mammals, ERVs are activated and produced in high quantities during the implantation of the embryo. Endogenous retroviruses are Retroviruses derived from ancient infections of Germ cells in Humans Mammals and other vertebrates as such their A viviparous Animal is an animal employing vivipary: the embryo develops inside the body of the mother as opposed to outside in an egg ( Ovipary On one hand they act as immunodepressors, and protect the embryo from the immune system of the mother and on the other hand viral fusion proteins cause the formation of the placental syncytium in order to limit the exchange of migratory cells between the developing embryo and the body of the mother, an epithelium won't do because certain blood cells are specialized to be able to insert themselves between adjacent epithelial cells. In Biology, a syncytium ( plural syncytia) is a large cell-like structure filled with Cytoplasm containing many nuclei In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body The ERV is a virus similar to HIV (the virus causing AIDS in humans). Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome The immunodepressive action was the initial normal behavior of the virus, similar to HIV. The fusion proteins was a way to spread the infection to other cells by simply merging them with the infected one (similar to HIV). It is believed that the ancestors of modern vivipary mammals evolved after an accidental infection of an ancestor with this virus, that permitted to the fetus to survive the immune system of the mother. A viviparous Animal is an animal employing vivipary: the embryo develops inside the body of the mother as opposed to outside in an egg ( Ovipary ^[5]

The human genome project found several thousand ERVs, which are organized into 24 families. ^[6]

Notes

References and external links

Obligate bacterial endosymbiosis in marine oligochaetes:

• Endosymbiotic sulphate-reducing and sulphide-oxidizing bacteria in an oligochaete worm. Dubilier N. , Mülders C. ,Ferdelman T. , De Beer D. ,Pernthaler A. ,Klein M. , Wagner M. , Erseus C. , Thiermann F. , Krieger J. , Giere O & Amann R. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11357130

Bacterial endosymbionts in echinoderms:

• Subcuticular bacteria from the brittle star Ophiactis balli (Echinodermata: Ophiuroidea) represent a new lineage of extracellular marine symbionts in the alpha subdivision of the class Proteobacteria. Burnett, W J and J D McKenzie http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=168468&rendertype=abstract

Symbiodinium dinoflagellate endosymbionts in marine metazoa and protists

• Excellent review paper covering the role of Symbiodinium in reef ecology and the current state of research: FLEXIBILITY AND SPECIFICITY IN CORAL-ALGAL SYMBIOSIS: Diversity, Ecology, and Biogeography of Symbiodinium. Andrew C. Baker, Annual Review of Ecology, Evolution, and Systematics 2003 34, 661-689

Obligate bacterial endosymbionts in insects:

• PLOS Biology Primer- Endosymbiosis: lessons in conflict resolution http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020068
• A general review of bacterial endosymbionts in insects. P. Baumann, N. A. Moran and L. Baumann, Bacteriocyte-associated endosymbionts of insects in M. Dworkin, ed. , The prokaryotes, Springer, New York, 2000. http://link.springer.de/link/service/books/10125/
• An excellent review of insect endosymbionts that focuses on genetic issues. Jennifer J. Wernegreen (2002), Genome evolution in bacterial endosymbionts of insects, Nature Reviews Genetics, 3, pp. 850-861. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12415315&dopt=Abstract
• A review article on aphids and their bacterial endosymbionts. A. E. Douglas (1998), Nutritional interactions in insect-microbial symbioses: Aphids and Their Symbiotic Bacteria Buchnera, Annual Reviews of Entomology, 43, pp. 17-37.
• Describes possible methods to control the human pathogen causing African sleeping sickness, which is transmitted by tsetse flies. Focuses on methods using the primary and secondary endosymbionts of the tsetse fly. Serap Aksoy, Ian Maudlin, Colin Dale, Alan S. Robinsonand and Scott L. O'Neill (2001), Prospects for control of African trypanosomiasis by tsetse vector, TRENDS in Parasitology, 17 (1), pp. 29-35. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11137738&dopt=Abstract
• Announces and analyzes the full genome sequence of Buchnera sp. APS, the endosymbiont of the pea aphid, and the first endosymbiont to have its genome sequenced. S. Shigenobu, H. Watanabe, M. Hattori, Y. Sakaki and H. Ishikawa (2000), Genome sequence of the endocellular bacterial symbiont of aphids Buchnera sp. APS, Nature, 407, pp. Nature is a prominent Scientific journal, first published on 4 November 1869 81-86. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10993077&dopt=Abstract
• An article that presents for the first time a theory on how obligate endosymbionts may have their genomes degraded, in a freely-available journal. Nancy A. Moran (1996), Accelerated evolution and Muller's ratchet in endosymbiotic bacteria, Proceedings of the National Academy of Sciences of the USA, 93, pp. The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United 2873-2878. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8610134&dopt=Abstract

See also

• Protobiont
• Endophyte

Protobionts are systems that are considered to have possibly been the precursors to Prokaryotic cells A protobiont is an aggregate of abiotically produced organic An endophyte is an Endosymbiont, often a Bacterium or Fungus, that lives within a Plant for at least part of its life without causing apparent

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