Buchnera aphidicola

{{Distinguish|Buchnera (plant)}}{{Short description|Species of bacterium}}

{{More citations needed|date=March 2012}}

{{Speciesbox

| image = Journal.pbio.0050126.g001.png

| image_caption = Buchnera aphidicola in a host cell

| image_alt = Buchnera aphidicola in a host cell

| genus = Buchnera

| parent_authority = Munson et al. 1991

| species = aphidicola

| authority = Munson et al. 1991{{cite web|title=Buchnera|url=https://lpsn.dsmz.de/genus/buchnera|website=List of Prokaryotic names with Standing in Nomenclature|accessdate=28 April 2018}}

}}

Buchnera aphidicola, a member of the Pseudomonadota and the only species in the genus Buchnera, is the primary endosymbiont of aphids, and has been studied in the pea aphid, Acyrthosiphon pisum.{{Cite journal|last=Douglas|first=A. E.|date=January 1998|title=Nutritional Interactions in Insect-Microbial Symbioses: Aphids and Their Symbiotic Bacteria Buchnera|url=http://www.annualreviews.org/doi/10.1146/annurev.ento.43.1.17|journal=Annual Review of Entomology|language=en|volume=43|issue=1|pages=17–37|doi=10.1146/annurev.ento.43.1.17|pmid=15012383|issn=0066-4170}} Buchnera is believed to have had a free-living, Gram-negative ancestor similar to a modern Enterobacterales, such as Escherichia coli. Buchnera is 3 μm in diameter and has some of the key characteristics of its 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 events due to strictly vertical transmission has seen the deletion of genes required for anaerobic respiration, the synthesis of amino sugars, fatty acids, phospholipids, and complex carbohydrates.{{Cite journal|last1=Gil|first1=Rosario|last2=Sabater-Muñoz|first2=Beatriz|last3=Latorre|first3=Amparo|last4=Silva|first4=Francisco J.|last5=Moya|first5=Andrés|date=2002|title=Extreme Genome Reduction in Buchnera spp.: Toward the Minimal Genome Needed for Symbiotic Life|url=https://www.jstor.org/stable/3058325|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=99|issue=7|pages=4454–4458|doi=10.1073/pnas.062067299|jstor=3058325|pmid=11904373|pmc=123669|issn=0027-8424|doi-access=free}} This has resulted not only in one of the smallest known genomes of any living organism, but also one of the most genetically stable.

The symbiotic relationship with aphids began between 160 million and 280 million years ago,{{cite journal|title=The Interactions of Allium sativum Leaf Agglutinin with a Chaperonin Group of Unique Receptor Protein Isolated from a Bacterial Endosymbiont of the Mustard Aphid|url=http://www.jbc.org/cgi/content/full/M401405200|pmid=15028723|doi=10.1074/jbc.M401405200|year=2004|last1=Banerjee|first1=S|last2=Hess|first2=D|last3=Majumder|first3=P|last4=Roy|first4=D|last5=Das|first5=S|volume=279|issue=22|pages=23782–9|journal=The Journal of Biological Chemistry|doi-access=free}} and has persisted through maternal transmission and cospeciation. Aphids have developed a bilobed bacteriome containing sixty to eighty bacteriocyte cells in which the life cycle of Buchnera associated with aphids is confined to.{{Cite journal|last=Baumann|first=Paul|title=Biology of Bacteriocyte-Associated Endosymbionts of Plant Sap-Sucking Insects|date=October 2005|url=http://www.annualreviews.org/doi/10.1146/annurev.micro.59.030804.121041|journal=Annual Review of Microbiology|language=en|volume=59|issue=1|pages=155–189|doi=10.1146/annurev.micro.59.030804.121041|pmid=16153167|issn=0066-4227}} A mature aphid may carry an estimated 5.6 × 10⁶ Buchnera cells. Buchnera has lost regulatory factors, allowing continuous overproduction of tryptophan and other amino acids. Each bacteriocyte contains multiple vesicles, symbiosomes derived from the cell membrane.