| agrobacterium tumefaciens | 155 | species | bacteria | bacteria | 358 |
| agrobacterium | 186 | genus | bacteria | | 357 |
| agreia | 5 | genus | bacteria | | 110934 |
| aggregatibacter | 18 | genus | bacteria | | 416916 |
| agarivorans | 8 | genus | bacteria | | 261825 |
| afifella | 1 | genus | bacteria | | 643217 |
| aestuariimicrobium | 1 | genus | bacteria | | 396388 |
| aestuariicola | 1 | genus | bacteria | | 483015 |
| aestuariibacter | 3 | genus | bacteria | | 249523 |
| aerosphaera | -3 | genus | bacteria | | 137460 |
| aeropyrum | 31 | genus | bacteria | | 56635 |
| aeromonas veronii bv. sobria | 14 | no rank | bacteria | bacteria | 114517 |
| aeromicrobium | 13 | genus | bacteria | | 2040 |
| aeroglyphus robustus | 4 | species | invertebrates | | 474095 |
| aeriscardovia | 6 | genus | bacteria | | 240233 |
| aequorivita | 2 | genus | bacteria | | 153265 |
| aelurostrongylus abstrusus | 16 | species | invertebrates | helminths | 321389 |
| advenella | 2 | genus | bacteria | | 290425 |
| adlercreutzia | 2 | genus | bacteria | | 447020 |
| adhaeribacter | 2 | genus | bacteria | | 299566 |
| adeno-associated virus - 2 | 79 | species | viruses | viruses | 10804 |
| adeno-associated virus | 134 | species | viruses | viruses | 272636 |
| actinotignum schaalii | 8 | species | bacteria | bacteria | 59505 |
| actinotelluria | -3 | genus | bacteria | | 333141 |
| actinotalea | 2 | genus | bacteria | | 458839 |
| actinosynnema | 12 | genus | bacteria | | 40566 |
| actinospica | 3 | genus | bacteria | | 414715 |
| actinopolyspora | 9 | genus | bacteria | | 1849 |
| actinopolymorpha | 3 | genus | bacteria | | 117156 |
| actinomycetospora | 1 | genus | bacteria | | 402649 |
| actinomadura meyerae | 1 | species | bacteria | bacteria | 240840 |
| actinokineospora | 7 | genus | bacteria | | 39845 |
| actinocorallia | 5 | genus | bacteria | | 58108 |
| actinocatenispora | 2 | genus | bacteria | | 390988 |
| actibacter | 1 | genus | bacteria | | 449462 |
| acrocarpospora | 2 | genus | bacteria | | 90974 |
| aciduliprofundum | 2 | genus | bacteria | | 379546 |
| acidothermus | 21 | genus | bacteria | | 28048 |
| acidomonas | 13 | genus | bacteria | | 34000 |
| acidocella | 8 | genus | bacteria | | 50709 |
| acidithiomicrobium | 1 | genus | bacteria | | 658428 |
| acidithiobacillus | 35 | genus | bacteria | | 119977 |
| acidisphaera | 9 | genus | bacteria | | 50714 |
| acidisoma | 1 | genus | bacteria | | 512381 |
| acidiphilium | 33 | genus | bacteria | | 522 |
| acidimicrobium | 16 | genus | bacteria | | 53634 |
| acidilobus | 5 | genus | bacteria | | 105850 |
| acidicaldus | 2 | genus | bacteria | | 368783 |
| acidianus | 36 | genus | bacteria | | 12914 |
| acidaminobacter | 5 | genus | bacteria | | 65402 |
| achromatium | 13 | genus | bacteria | | 44937 |
| acholeplasma laidlawii | 67 | species | bacteria | bacteria | 2148 |
| acetomicrobium | 4 | genus | bacteria | | 49894 |
| acetohalobium | 7 | genus | bacteria | | 28186 |
| acetobacterium | 40 | genus | bacteria | | 33951 |
| acetobacter | 88 | genus | bacteria | | 434 |
| acetitomaculum | 9 | genus | bacteria | | 31980 |
| acetanaerobacterium | 2 | genus | bacteria | | 258514 |
| acaryochloris | 21 | genus | bacteria | | 155977 |
| acanthamoeba lenticulata | 6 | species | invertebrates | protozoa | 29196 |
| [candida] palmioleophila | 2 | species | plants | fungi | 45574 |
| [candida] nivariensis | 6 | species | plants | fungi | 418086 |
| [candida] membranifaciens | 6 | species | plants | fungi | 45567 |
| [candida] inconspicua | 13 | species | plants | fungi | 52247 |
| [candida] ethanolica | 2 | species | plants | fungi | 52256 |
| [candida] bracarensis | 3 | species | plants | fungi | 273131 |