''Buchnera aphidicola'', a member of the

Pseudomonadota Pseudomonadota (synonym Proteobacteria) is a major phylum of Gram-negative bacteria. The renaming of phyla in 2021 remains controversial among microbiologists, many of whom continue to use the earlier names of long standing in the literature. Th ...

and the only species in the genus ''Buchnera'', is the primary

endosymbiont An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship. (The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within ...

aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...

s, and has been studied in the pea aphid, ''

Acyrthosiphon pisum ''Acyrthosiphon pisum'', commonly known as the pea aphid (and colloquially known as the green dolphin, pea louse, and clover louse), is a sap-sucking insect in the family Aphididae. It feeds on several species of legumes (plant family Fabaceae) ...

''. ''Buchnera'' is believed to have had a free-living,

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...

ancestor similar to a modern

Enterobacterales Enterobacterales is an order of Gram-negative, non-spore forming, facultatively anaerobic, rod-shaped bacteria with the class Gammaproteobacteria. The type genus of this order is ''Enterobacter.'' The name Enterobacterales is derived from th ...

, such as ''Escherichia coli''. ''Buchnera'' is 3 µm in diameter and has some of the key characteristics of their Enterobacterales relatives, such as a Gram-negative cell wall. However, unlike most other Gram-negative bacteria, ''Buchnera'' lacks the genes to produce lipopolysaccharides for its outer membrane. The long association with aphids and the limitation of

crossover Crossover may refer to: Entertainment Albums and songs * ''Cross Over'' (Dan Peek album) * ''Crossover'' (Dirty Rotten Imbeciles album), 1987 * ''Crossover'' (Intrigue album) * ''Crossover'' (Hitomi Shimatani album) * ''Crossover'' (Yoshino ...

events due to strictly

vertical transmission Vertical transmission of symbionts is the transfer of a microbial symbiont from the parent directly to the offspring. Many metazoan species carry symbiotic bacteria which play a mutualistic, commensal, or parasitic role. A symbiont is acquir ...

has seen the deletion of genes required for

anaerobic respiration Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain. In aerobic organisms undergoing r ...

, the synthesis of

amino sugar In organic chemistry, an amino sugar (or more technically a 2-amino-2-deoxysugar) is a sugar molecule in which a hydroxyl group has been replaced with an amine group. More than 60 amino sugars are known, with one of the most abundant being ''N''- ...

fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...

phospholipid Phospholipids, are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...

s, and complex

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may o ...

s. This has resulted not only in one of the smallest known

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...

s of any living organism, but also one of the most genetically stable. The

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or para ...

relationship with aphids began between 160 million and 280 million years ago, and has persisted through maternal transmission and cospeciation. Aphids have developed a bilobed bacteriome containing sixty to eighty

bacteriocyte A bacteriocyte ( Greek for ''bacteria cell''), also known as a mycetocyte, is a specialized adipocyte found primarily in certain insect groups such as aphids, tsetse flies, German cockroaches, weevils. These cells contain endosymbiotic organism ...

cells in which the life cycle of ''Buchnera'' associated with aphids is confined to. A mature

may carry an estimated 5.6 × 10⁶ ''Buchnera'' cells. ''Buchnera'' has lost regulatory factors, allowing continuous overproduction of

tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic ...

and other

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...

s. Each bacteriocyte contains multiple

vesicles Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like features o ...

, symbiosomes derived from the

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (t ...

Genome

The sizes of various ''Buchnera'' genomes are in the range of 600 to 650 kb and encode on the order of 500 to 560 proteins. Many contain also one or two plasmids (2.3 to 11 kb in size). As with many

s, Abbot and Moran 2002 find ''Buchnera'' in ''

Pemphigus Pemphigus ( or ) is a rare group of blistering autoimmune diseases that affect the skin and mucous membranes. The name is derived from the Greek root ''pemphix'', meaning "pustule". In pemphigus, autoantibodies form against desmoglein, whic ...

obesinymphae'' to be undergoing relatively high

genetic drift Genetic drift, also known as allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and there ...

(i.e., relative to all organisms). This is evidenced by extremely low

gene polymorphism A gene is said to be polymorphic if more than one allele occupies that gene's locus within a population. In addition to having more than one allele at a specific locus, each allele must also occur in the population at a rate of at least 1% to g ...

and some nonsynonymous variants.

''Buchnera'' and plant viruses

''Buchnera'' also increases the transmission of

plant virus Plant viruses are viruses that affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses can be pathogenic to higher plants. ...

es by producing symbionin, a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

that binds to the

viral coat A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes. Numerous human pathogenic viruses in circulation are encas ...

and protects it inside the aphid. This makes it more likely that the virion will survive and be able to infect another plant when the aphid next feeds.

History

''Buchnera'' was named after by Paul Baumann and his graduate student, and the first molecular characterization of a symbiotic bacterium was carried out by Baumann, using ''Buchnera''. The initial studies on ''Buchnera'' later led to studies on symbionts of many groups of insects, pursued by numerous investigators, including Paul and Linda Baumann, Nancy Moran, Serap Aksoy, and Roy Gross, who together investigated symbionts of aphids, tsetse flies, ants, leafhoppers, mealybugs, whiteflies, psyllids, and others.

References

* *

External links

''Buchnera'' Genome Projects
(fro
Genomes OnLine Database

Comparative Analysis of ''Buchnera'' Genomes
(at DOE's IMG system) {{Taxonbar, from1=Q383453, from2=Q18606581 Aphids Enterobacterales