| propioniferax | 6 | genus | bacteria | | 53456 |
| propionimicrobium | 2 | genus | bacteria | | 203133 |
| propionispira | 3 | genus | bacteria | | 84034 |
| propionispora | 3 | genus | bacteria | | 112902 |
| propionivibrio | 4 | genus | bacteria | | 83766 |
| prosthecobacter | 19 | genus | bacteria | | 48463 |
| prosthecochloris | 43 | genus | bacteria | | 1101 |
| prosthecomicrobium | 8 | genus | bacteria | | 81894 |
| protaminobacter | 12 | genus | bacteria | | 126824 |
| proteiniborus | 6 | genus | bacteria | | 415014 |
| proteinimicrobium | -3 | genus | bacteria | | 448157 |
| proteiniphilum | 2 | genus | bacteria | | 294702 |
| proteocatella | -3 | genus | bacteria | | 181069 |
| prototheca zopfii var. portoricensis | 1 | varietas | plants | | 283961 |
| pseudacidovorax | 1 | genus | bacteria | | 433923 |
| pseudallescheria angusta | 2 | species | plants | fungi | 70116 |
| pseudallescheria ellipsoidea | 3 | species | plants | fungi | 45271 |
| pseudaminobacter | 11 | genus | bacteria | | 93368 |
| pseudanabaena | 27 | genus | bacteria | | 1152 |
| pseudaspidodera jnanendre | -3 | species | | helminths | |
| pseudaspidodera pavonis | -3 | species | | helminths | |
| pseudidiomarina | 3 | genus | bacteria | | 337249 |
| pseudobacillus | -3 | genus | bacteria | | 108525 |
| pseudoburkholderia | -3 | genus | bacteria | | 383687 |
| pseudobutyrivibrio | 7 | genus | bacteria | | 46205 |
| pseudobutyrivibrio xylanivorans | 4 | species | bacteria | bacteria | 185007 |
| pseudochrobactrum | 3 | genus | bacteria | | 354349 |
| pseudoclavibacter | 4 | genus | bacteria | | 255204 |
| pseudogluconobacter | 2 | genus | bacteria | | 133920 |
| pseudolabrys | 1 | genus | bacteria | | 556257 |
| pseudomonas meridiana | 1 | species | bacteria | bacteria | 219573 |
| pseudomonas monteilii | 7 | species | bacteria | bacteria | 76759 |
| pseudomonas synxantha | 8 | species | bacteria | bacteria | 47883 |
| pseudonocardia | 24 | genus | bacteria | | 1847 |
| pseudophormidium | 1 | genus | bacteria | | 268156 |
| pseudorhodobacter | 2 | genus | bacteria | | 238783 |
| pseudoroseobacter | -3 | genus | bacteria | | 343404 |
| pseudoruegeria | 2 | genus | bacteria | | 311411 |
| pseudosphingobacterium | 1 | genus | bacteria | | 407021 |
| pseudospirillum | 2 | genus | bacteria | | 196078 |
| pseudosporangium | 1 | genus | bacteria | | 439698 |
| pseudovibrio | 6 | genus | bacteria | | 258255 |
| pseudoxanthobacter | 1 | genus | bacteria | | 433838 |
| pseudoxanthomonas | 13 | genus | bacteria | | 83618 |
| pseudozobellia | 1 | genus | bacteria | | 633413 |
| psychrilyobacter | 1 | genus | bacteria | | 623282 |
| psychrobacter pulmonis | 1 | species | bacteria | bacteria | 228654 |
| psychroflexus | 6 | genus | bacteria | | 83612 |
| psychromonas | 10 | genus | bacteria | | 67572 |
| psychroserpens | 6 | genus | bacteria | | 49277 |
| psychrosinus | 1 | genus | bacteria | | 552808 |
| pullulanibacillus | 1 | genus | bacteria | | 475230 |
| puniceicoccus | 1 | genus | bacteria | | 388745 |
| pusillimonas | 2 | genus | bacteria | | 305976 |
| pyramidobacter | 2 | genus | bacteria | | 638847 |
| pyrobaculum | 41 | genus | bacteria | | 2276 |
| pyrococcus | 103 | genus | bacteria | | 2260 |
| pyrodictium | 26 | genus | bacteria | | 2308 |
| pyrolobus | 5 | genus | bacteria | | 54251 |
| pyxidicoccus | 1 | genus | bacteria | | 224458 |
| quadrisphaera | 2 | genus | bacteria | | 317661 |
| quatrionicoccus | 2 | genus | bacteria | | 138117 |
| quinella | 3 | genus | bacteria | | 1567 |
| radiocystis | 4 | genus | bacteria | | 442397 |
| rahnella | 23 | genus | bacteria | | 34037 |
| raillietia auris | 6 | species | | | |
| raillietia hopkinsi | -3 | species | | | |
| raillietina cesticillus | 12 | species | | helminths | 246978 |
| raillietina georgiensis | 2 | species | | helminths | |
| raillietina magninumida | -3 | species | | helminths | |
| raillietina micracantha | 2 | species | invertebrates | helminths | 227345 |
| raillietina ransomi | -3 | species | | helminths | |
| raillietina williamsi | 1 | species | | helminths | |
| ramlibacter | 5 | genus | bacteria | | 174951 |
| raoultella | 11 | genus | bacteria | | 160674 |
| raoultella terrigena | 16 | species | bacteria | bacteria | 577 |
| raphidiopsis | 12 | genus | bacteria | | 244599 |
| rapidithrix | 3 | genus | bacteria | | 413963 |
| rarobacter | 9 | genus | bacteria | | 13242 |
| rasamsonia argillacea | 3 | species | plants | fungi | 69808 |
| reichenbachiella | 4 | genus | bacteria | | 156993 |
| reichenowia | 2 | genus | bacteria | | 237321 |
| reinekea | 2 | genus | bacteria | | 230494 |
| retortamonas caviae | -3 | species | | protozoa | |
| retortamonas cuniculi | -3 | species | | protozoa | |
| retortamonas ovis | -3 | species | | protozoa | |
| retortamonas sinensis | -3 | species | | protozoa | |
| rexia | 2 | genus | bacteria | | 262901 |
| rhabditis axei | 1 | species | | helminths | |
| rhabditis clavopapillata | -3 | species | | helminths | |
| rhabditis gingivalis | -3 | species | | helminths | |
| rhabditis macrocerca | -3 | species | | helminths | |
| rhabdochromatium | 2 | genus | bacteria | | 48728 |
| rhabdoderma | 3 | genus | bacteria | | 262065 |
| rheinheimera | 8 | genus | bacteria | | 67575 |
| rhinocladiella basitona | 2 | species | plants | fungi | 215248 |
| rhodanobacter | 10 | genus | bacteria | | 75309 |
| rhodobaca | 4 | genus | bacteria | | 119541 |
| rhodobacter | 151 | genus | bacteria | | 1060 |
| rhodobium | 12 | genus | bacteria | | 34016 |