| Spezies | Risiko- gruppe | Bemer- kungen | Status |
| Obesumbacterium | |||
| Obesumbacterium proteus | 1 | ||
| Oblitimonas | |||
| Oblitimonas alkaliphila | 1 | + | neu |
| Occallatibacter | |||
| Occallatibacter riparius | 1 | neu | |
| Occallatibacter savannae | 1 | neu | |
| Oceanibacterium | |||
| Oceanibacterium hippocampi | 1 | ||
| Oceanibaculum | |||
| Oceanibaculum indicum | 1 | ||
| Oceanibaculum nanhaiense | 1 | neu | |
| Oceanibaculum pacificum | 1 | ||
| Oceanibulbus | |||
| Oceanibulbus indolifex → Sulfitobacter indolifex | Umb. | ||
| Oceanicaulis | |||
| Oceanicaulis alexandrii | 1 | ||
| Oceanicaulis stylophorae | 1 | ||
| Oceanicella | |||
| Oceanicella actignis | 1 | ||
| Oceanicola | |||
| Oceanicola antarcticus → Pseudooceanicola antarcticus | Umb. | ||
| Oceanicola batsensis → Pseudooceanicola batsensis | Umb. | ||
| Oceanicola flagellatus → Pseudooceanicola flagellatus | Umb. | ||
| Oceanicola granulosus | 1 | ||
| Oceanicola litoreus | 1 | ||
| Oceanicola marinus → Pseudooceanicola marinus | Umb. | ||
| Oceanicola nanhaiensis → Pseudooceanicola nanhaiensis | Umb. | ||
| Oceanicola nitratireducens → Pseudooceanicola nitratireducens | Umb. | ||
| Oceanicola pacificus | 1 | ||
| Oceaniglobus | |||
| Oceaniglobus indicus | 1 | neu | |
| Oceanihabitans | |||
| Oceanihabitans sediminis | 1 | neu | |
| Oceanimonas | |||
| Oceanimonas baumannii | 1 | ||
| Oceanimonas doudoroffii (Pseudomonas doudoroffii) | 1 | ||
| Oceanimonas smirnovii | 1 | ||
| Oceanirhabdus | |||
| Oceanirhabdus sediminicola | 1 | ||
| Oceaniserpentilla | |||
| Oceaniserpentilla haliotis | 1 | ||
| Oceanisphaera | |||
| Oceanisphaera arctica | 1 | ||
| Oceanisphaera donghaensis | 1 | ||
| Oceanisphaera litoralis | 1 | ||
| Oceanisphaera marina | 1 | neu | |
| Oceanisphaera ostreae | 1 | ||
| Oceanisphaera profunda | 1 | ||
| Oceanisphaera psychrotolerans | 1 | neu | |
| Oceanisphaera sediminis | 1 | ||
| Oceanispirochaeta | |||
| Oceanispirochaeta litoralis (Spirochaeta litoralis) | 1 | Umb. | |
| Oceanispirochaeta sediminicola | 1 | neu | |
| Oceanitalea | |||
| Oceanitalea nanhaiensis – synonym: Georgenia satyanarayanai | Umb. | ||
| Oceanithermus | |||
| Oceanithermus desulfurans | 1 | ||
| Oceanithermus profundus | 1 | ||
| Oceanivirga | |||
| Oceanivirga salmonicida | 2 | t | neu |
| Oceanobacillus | |||
| Oceanobacillus arenosus | 1 | neu | |
| Oceanobacillus bengalensis | 1 | neu | |
| Oceanobacillus caeni | 1 | ||
| Oceanobacillus chironomi | 1 | ||
| Oceanobacillus chungangensis | 1 | ||
| Oceanobacillus damuensis | 1 | neu | |
| Oceanobacillus halophilus | 1 | neu | |
| Oceanobacillus iheyensis | 1 | ||
| Oceanobacillus indicireducens | 1 | ||
| Oceanobacillus kapialis | 1 | ||
| Oceanobacillus kimchii | 1 | ||
| Oceanobacillus limi | 1 | ||
| Oceanobacillus locisalsi | 1 | ||
| Oceanobacillus longus | 1 | neu | |
| Oceanobacillus luteolus | 1 | ||
| Oceanobacillus neutriphilus | 1 | ||
| Oceanobacillus oncorhynchi subsp. incaldanensis | 1 | ||
| Oceanobacillus oncorhynchi subsp. oncorhynchi | 1 | ||
| Oceanobacillus pacificus | 1 | ||
| Oceanobacillus picturae (Virgibacillus picturae) | 1 | ||
| Oceanobacillus polygoni | 1 | ||
| Oceanobacillus profundus | 1 | ||
| Oceanobacillus rekensis | 1 | neu | |
| Oceanobacillus sojae | 1 | ||
| Oceanobacter | |||
| Oceanobacter kriegii (Oceanospirillum kriegii) | 1 | ||
| Oceanococcus | |||
| Oceanococcus atlanticus | 1 | ||
| Oceanospirillum | |||
| Oceanospirillum beijerinckii (Oceanospirillum beijerinckii subsp. beijerinckii, Oceanospirillum beijerinckii subsp. pelagicum, Oceanospirillum pelagicum) | 1 | ||
| Oceanospirillum beijerinckii subsp. beijerinckii → Oceanospirillum beijerinckii | |||
| Oceanospirillum beijerinckii subsp. pelagicum (Oceanospirillum pelagicum) → Oceanospirillum beijerinckii | |||
| Oceanospirillum commune = Marinomonas communis (Alteromonas communis) | 1 | ||
| Oceanospirillum hiroshimense → Oceanospirillum maris | |||
| Oceanospirillum jannaschii → Marinobacterium jannaschii | |||
| Oceanospirillum japonicum → Pseudospirillum japonicum | |||
| Oceanospirillum kriegii → Oceanobacter kriegii | |||
| Oceanospirillum linum | 1 | ||
| Oceanospirillum maris (Oceanospirillum maris subsp. hiroshimense, Oceanospirillum hiroshimense, Oceanospirillum maris subsp. maris, Oceanospirillum maris subsp. williamsae) | 1 | ||
| Oceanospirillum maris subsp. hiroshimense (Oceanospirillum hiroshimense) → Oceanospirillum maris | |||
| Oceanospirillum maris subsp. maris → Oceanospirillum maris | |||
| Oceanospirillum maris subsp. williamsae → Oceanospirillum maris | |||
| Oceanospirillum minutulum → Marinospirillum minutulum | |||
| Oceanospirillum multiglobuliferum | 1 | ||
| Oceanospirillum pelagicum → Oceanospirillum beijerinckii | |||
| Oceanospirillum pusillum → Terasakiella pusilla | |||
| Oceanospirillum sanctuarii | 1 | neu | |
| Oceanospirillum vagum = Marinomonas vaga (Alteromonas vaga) | 1 | ||
| Oceanotoga | |||
| Oceanotoga teriensis | 1 | ||
| Ochrobactrum | |||
| Ochrobactrum anthropi | 2 | TA, ht | |
| Ochrobactrum ciceri | 1 | ||
| Ochrobactrum cytisi | 1 | ||
| Ochrobactrum daejeonense | 1 | ||
| Ochrobactrum endophyticum | 1 | neu | |
| Ochrobactrum gallinifaecis | 1 | ||
| Ochrobactrum grignonense | 1 | ||
| Ochrobactrum haematophilum | 1 | + | |
| Ochrobactrum intermedium | 2 | ||
| Ochrobactrum lupini | 1 | ||
| Ochrobactrum oryzae | 1 | ||
| Ochrobactrum pecoris | 1 | t+ | |
| Ochrobactrum pituitosum | 1 | ||
| Ochrobactrum pseudintermedium | 1 | + | |
| Ochrobactrum pseudogrignonense | 1 | + | |
| Ochrobactrum rhizosphaerae | 1 | ||
| Ochrobactrum thiophenivorans | 1 | ||
| Ochrobactrum tritici | 1 | ||
| Octadecabacter | |||
| Octadecabacter antarcticus | 1 | ||
| Octadecabacter arcticus | 1 | ||
| Octadecabacter ascidiaceicola | 1 | neu | |
| Octadecabacter jejudonensis → Pseudooctadecabacter jejudonensis | Umb. | ||
| Octadecabacter ponticola | 1 | neu | |
| Octadecabacter temperatus | 1 | neu | |
| Odoribacter | |||
| Odoribacter denticanis | 2 | t | |
| Odoribacter laneus | 1 | ||
| Odoribacter splanchnicus (Bacteroides splanchnicus) | 2 | ||
| Oenococcus | |||
| Oenococcus alcoholitolerans | 1 | neu | |
| Oenococcus kitaharae | 1 | ||
| Oenococcus oeni (Leuconostoc oenos) | 1 | ||
| Oerskovia | |||
| Oerskovia enterophila (Promicromonospora enterophila) | 1 | ||
| Oerskovia jenensis | 1 | ||
| Oerskovia paurometabola | 1 | ||
| Oerskovia turbata | 1 | + | |
| Oerskovia xanthineolytica – synonym: Cellulomonas cellulans → Cellulosimicrobium cellulans | |||
| Oharaeibacter | |||
| Oharaeibacter diazotrophicus | 1 | neu | |
| Ohtaekwangia | |||
| Ohtaekwangia koreensis | 1 | ||
| Ohtaekwangia kribbensis | 1 | ||
| Okibacterium | |||
| Okibacterium endophyticum | 1 | neu | |
| Okibacterium fritillariae | 1 | ||
| Oleiagrimonas | |||
| Oleiagrimonas citrea | 1 | neu | |
| Oleiagrimonas soli | 1 | neu | |
| Oleibacter | |||
| Oleibacter marinus | 1 | ||
| Oleiphilus | |||
| Oleiphilus messinensis | 1 | ||
| Oleispira | |||
| Oleispira antarctica | 1 | ||
| Oleispira lenta | 1 | ||
| Oligella | |||
| Oligella ureolytica | 1 | + | |
| Oligella urethralis (Moraxella urethralis) | 1 | ht+ | |
| Oligoflexus | |||
| Oligoflexus tunisiensis | 1 | neu | |
| Oligosphaera | |||
| Oligosphaera ethanolica | 1 | ||
| Oligotropha | |||
| Oligotropha carboxidovorans | 1 | ||
| Olivibacter | |||
| Olivibacter composti | 1 | neu | |
| Olivibacter ginsengisoli | 1 | ||
| Olivibacter jilunii | 1 | ||
| Olivibacter oleidegradans | 1 | ||
| Olivibacter sitiensis | 1 | ||
| Olivibacter soli | 1 | ||
| Olivibacter terrae | 1 | ||
| Olleya | |||
| Olleya algicola | 1 | neu | |
| Olleya aquimaris | 1 | ||
| Olleya marilimosa | 1 | ||
| Olleya namhaensis | 1 | ||
| Olsenella | |||
| Olsenella profusa | 2 | ||
| Olsenella scatoligenes | 1 | neu | |
| Olsenella uli (Lactobacillus uli) | 2 | ||
| Olsenella umbonata | 1 | ||
| Opitutus | |||
| Opitutus terrae | 1 | ||
| Orbus | |||
| Orbus hercynius | 1 | ||
| Orbus sasakiae | 1 | ||
| Orenia | |||
| Orenia chitinitropha | 1 | neu | |
| Orenia marismortui (Sporohalobacter marismortui) | 1 | ||
| Orenia salinaria | 1 | ||
| Orenia sivashensis | 1 | ||
| Oribacterium | |||
| Oribacterium asaccharolyticum | 1 | neu | |
| Oribacterium parvum | 1 | neu | |
| Oribacterium sinus | 1 | + | |
| Oribaculum → Porphyromonas | |||
| Oribaculum catoniae → Porphyromonas catoniae | |||
| Oricola | |||
| Oricola cellulosilytica | 1 | neu | |
| Orientia | |||
| Orientia tsutsugamushi (Rickettsia tsutsugamushi) | 3 | Z | |
| Ornatilinea | |||
| Ornatilinea apprima | 1 | ||
| Ornithinibacillus | |||
| Ornithinibacillus bavariensis | 1 | ||
| Ornithinibacillus californiensis | 1 | ||
| Ornithinibacillus contaminans | 1 | ||
| Ornithinibacillus halophilus | 1 | ||
| Ornithinibacillus halotolerans | 1 | ||
| Ornithinibacillus heyuanensis | 1 | neu | |
| Ornithinibacillus scapharcae | 1 | n+ | |
| Ornithinibacter | |||
| Ornithinibacter aureus | 1 | ||
| Ornithinicoccus | |||
| Ornithinicoccus halotolerans | 1 | neu | |
| Ornithinicoccus hortensis | 1 | ||
| Ornithinimicrobium | |||
| Ornithinimicrobium algicola | 1 | neu | |
| Ornithinimicrobium flavum | 1 | neu | |
| Ornithinimicrobium humiphilum | 1 | ||
| Ornithinimicrobium kibberense | 1 | ||
| Ornithinimicrobium murale | 1 | ||
| Ornithinimicrobium pekingense | 1 | ||
| Ornithinimicrobium tianjinense | 1 | ||
| Ornithobacterium | |||
| Ornithobacterium rhinotracheale | 2 | t | |
| Oryzihumus | |||
| Oryzihumus leptocrescens | 1 | ||
| Oryzihumus soli | 1 | neu | |
| Oryzihumus terrae | 1 | neu | |
| Oryzisolibacter | |||
| Oryzisolibacter propanilivorax | 1 | neu | |
| Oryzobacter | |||
| Oryzobacter terrae | 1 | neu | |
| Oryzomicrobium | |||
| Oryzomicrobium terrae | 1 | neu | |
| Oscillibacter | |||
| Oscillibacter ruminantium | 1 | ||
| Oscillibacter valericigenes | 1 | ||
| Oscillochloris | |||
| Oscillochloris chrysea | 1 | ||
| Oscillochloris trichoides | 1 | ||
| Oscillospira | |||
| Oscillospira guilliermondi | 1 | ||
| Otariodibacter | |||
| Otariodibacter oris | 1 | ||
| Ottowia | |||
| Ottowia beijingensis | 1 | ||
| Ottowia pentelensis | 1 | ||
| Ottowia thiooxydans | 1 | ||
| Owenweeksia | |||
| Owenweeksia hongkongensis | 1 | ||
| Oxalicibacterium | |||
| Oxalicibacterium faecigallinarum | 1 | ||
| Oxalicibacterium flavum | 1 | ||
| Oxalicibacterium horti | 1 | ||
| Oxalicibacterium solurbis | 1 | ||
| Oxalobacter | |||
| Oxalobacter formigenes | 1 | ||
| Oxalobacter vibrioformis | 1 | ||
| Oxalophagus | |||
| Oxalophagus oxalicus (Clostridium oxalicum) | 1 | ||
| Oxobacter | |||
| Oxobacter pfennigii (Clostridium pfennigii) | 1 |