Abiotrophia
defectiva

Acetobacter
aceti - cerevisiae - cibinongensis - estunensis - indonesiensis - lovaniensis - malorum - oeni - orientalis - orleanensis - pasteurianus - peroxydans - pomorum - sp. - tropicalis

Acetomicrobium
flavidum

Achromobacter
cholinophagum - denitrificans - hartlebii - insolitus - pestifer - piechaudii - ruhlandii - spanios - xylosoxidans

Achromobacter-like
group

Acidomonas
methanolica

Acidovorax
avenae - delafieldii - facilis - konjaci - temperans

Acinetobacter
baumannii - calcoaceticus - haemolyticus - johnsonii - junii - lwoffii - parvus - radioresistens - schindleri - sp. - ursingii

Actinobacillus
equuli - lignieresii

Actinobaculum
schaalii - suis

Actinomyces
europaeus - graevenitzii - hongkongensis - meyeri - neuii - odontolyticus - radingae - turicensis

Advenella
incenata - sp.

Aequorivita
antarctica - lipolytica - sublithincola

Aeriscardovia
aeriphila

Aerococcus
christensenii - urinae - urinaeequi - viridans

Aeromicrobium
erythreum - fastidiosum - marinum

Aeromonas
allosaccharophila - bestiarum - caviae - culicicola - encheleia - enteropelogenes - eucrenophila - hydrophila - ichthiosmia - jandaei - media - molluscorum - popoffii - salmonicida - schubertii - simiae - sobria - sp. - veronii

Afipia
broomeae - clevelandensis - felis

Agarivorans
albus

Agreia
pratensis

Agrobacterium
azotophilum - luteum - sanguineum - sp.

Agromonas
oligotrophica

Agromyces
cerinus - fucosus - hippuratus - mediolanus - ramosus - ulmi

Ahrensia
kielensis

Alcaligenes
aquatilis - defragrans - faecalis

Alginovibrio
immotus

Algoriphagus
antarcticus - aquimarinus - chordae - halophilus - ratkowskyi - winogradskyi

Alicyclobacillus
acidocaldarius - acidoterrestris - cycloheptanicus

Alkalibacillus
haloalkaliphilus

Allomonas
enterica

Alteromonas
addita - hispanica - macleodii - marina - sp. - stellipolaris

Aminobacter
aminovorans

Aminomonas
aminovorus

Amphibacillus
xylanus

Amycolatopsis
lurida

Anaerobiospirillum
succiniciproducens

Anaerococcus
tetradius

Ancylobacter
aquaticus

Aneurinibacillus
aneurinilyticus - migulanus - terranovensis - thermoaerophilus

Anoxybacillus
contaminans - flavithermus

Aquabacter
spiritensis

Aquamicrobium
defluvii

Aquaspirillum
itersonii - peregrinum - polymorphum - putridiconchylium - serpens

Aquicella
lusitana - siphonis

Aquiflexum
balticum

Aquimarina
muelleri

Arcanobacterium
bernardiae - haemolyticum - phocae - pluranimalium - pyogenes

Arcicella
aquatica

Arcobacter
butzleri - cibarius - cryaerophilus - nitrofigilis - skirrowii

Arenibacter
latericius - palladensis

Arsenophonus
nasoniae

Arthrobacter
agilis - atrocyaneus - aurescens - castelli - citreus - creatinolyticus - crystallopoietes - duodecadis - gandavensis - globiformis - histidinolovorans - ilicis - monumenti - mysorens - nicotianae - nicotinovorans - oxydans - parietes - pascens - pigmenti - polychromogenes - protophormiae - psychrophenolicus - ramosus - rhombi - sp. - stackebrandtii - sulfureus - tecti - tumbae - uratoxydans - ureafaciens - viscosus

Asaia
bogorensis - siamensis

Atopobium
minutum - rimae

Azoarcus
communis - indigens

Azohydromonas
australica - lata

Azomonas
agilis - macrocytogenes

Azonexus
fungiphilus

Azorhizobium
caulinodans

Azorhizophilus
paspali

Azospira
oryzae

Azospirillum
amazonense - brasilense - camarguensis - halopraeferens - irakense - lipoferum

Azotobacter
beijerinckii - chroococcum - nigricans - vinelandii

Azovibrio
restrictus