| mycoplasma meleagridis | 18 | species | bacteria | bacteria | 29561 |
| mycoplasma mycoides | 38 | species | bacteria | bacteria | 2102 |
| mycoplasma mycoides subsp. mycoides | 26 | subspecies | bacteria | bacteria | 2103 |
| mycoplasma ovipneumoniae | 13 | species | bacteria | bacteria | 29562 |
| mycoplasma pneumoniae | 93 | species | bacteria | bacteria | 2104 |
| mycoplasma putrefaciens | 12 | species | bacteria | bacteria | 2123 |
| mycoplasma salivarium | 17 | species | bacteria | bacteria | 2124 |
| mycoplasma suis | 19 | species | bacteria | bacteria | 57372 |
| mycoplasma synoviae | 30 | species | bacteria | bacteria | 2109 |
| myobiidae | 7 | family | | | 1046726 |
| myriodontium keratinophilum | 3 | species | plants | fungi | 150376 |
| myroides | 10 | genus | bacteria | | 76831 |
| myroides odoratus | 15 | species | bacteria | bacteria | 256 |
| myxobolus cartilaginis | -3 | species | | | |
| myxobolus cerebralis | 31 | species | invertebrates | | 59783 |
| myxobolus dujardini | -3 | species | invertebrates | | 378072 |
| myxococcus | 99 | genus | bacteria | | 32 |
| myxoma virus | 59 | species | viruses | viruses | 10273 |
| naegleria fowleri | 33 | species | invertebrates | protozoa | 5763 |
| nairovirus | 24 | genus | viruses | | 11592 |
| nanophyetus salmincola | 10 | species | invertebrates | helminths | 240278 |
| nanophyetus schkhobalowi | -3 | species | | helminths | 1834224 |
| necator americanus | 46 | species | invertebrates | helminths | 51031 |
| neisseria | 163 | genus | bacteria | | 482 |
| neisseria cinerea | 17 | species | bacteria | bacteria | 483 |
| neisseria elongata | 9 | species | bacteria | bacteria | 495 |
| neisseria flava | 7 | species | bacteria | bacteria | 34026 |
| neisseria flavescens | 11 | species | bacteria | bacteria | 484 |
| neisseria gonorrhoeae | 136 | species | bacteria | bacteria | 485 |
| neisseria gonorrhoeae tcdc-ng08107 | 1 | no rank | bacteria | bacteria | 940296 |
| neisseria lactamica | 31 | species | bacteria | bacteria | 486 |
| neisseria meningitidis | 130 | species | bacteria | bacteria | 487 |
| neisseria meningitidis k1207 | -3 | no rank | bacteria | bacteria | 768485 |
| neisseria mucosa | 14 | species | bacteria | bacteria | 488 |
| neisseria perflava | 15 | species | bacteria | bacteria | 33053 |
| neisseria sicca | 14 | species | bacteria | bacteria | 490 |
| neisseria subflava | 14 | species | bacteria | bacteria | 28449 |
| neisseria weaveri | 6 | species | bacteria | bacteria | 28091 |
| nematodirus abnormalis | 2 | species | | helminths | |
| nematodirus andreevi | -3 | species | | helminths | |
| nematodirus aspinosus | -3 | species | | helminths | |
| nematodirus battus | 19 | species | invertebrates | helminths | 28839 |
| nematodirus filicollis | 11 | species | invertebrates | helminths | 61840 |
| nematodirus hsuei | -3 | species | | helminths | |
| nematodirus lamae | 2 | species | | helminths | |
| nematodirus leporis | 1 | species | | helminths | |
| nematodirus odocoilei | 2 | species | | helminths | |
| nematodirus oiratianus | 2 | species | invertebrates | helminths | 94037 |
| nematodirus spathiger | 16 | species | invertebrates | helminths | 61841 |
| nematodirus tarandi | -3 | species | | helminths | |
| neobalantidium coli | 17 | species | invertebrates | protozoa | 71585 |
| neodeightonia subglobosa | 1 | species | plants | fungi | 371117 |
| neodiplostomum | 9 | genus | invertebrates | | 84101 |
| neodiplostomum multicellulata | -3 | species | | helminths | |
| neodiplostomum perlatum | 1 | species | | helminths | |
| neofusicoccum mangiferae | 16 | species | plants | fungi | 463686 |
| neorickettsia | 20 | genus | bacteria | | 33993 |
| neorickettsia elokominica | -3 | species | | bacteria | |
| neorickettsia helminthoeca | 14 | species | bacteria | bacteria | 33994 |
| neorickettsia risticii | 24 | species | bacteria | bacteria | 950 |
| neorickettsia sennetsu | 18 | species | bacteria | bacteria | 951 |
| neoschongastia americana | 4 | species | | | |
| neoscytalidium hyalinum | 16 | species | plants | fungi | 1451147 |
| neospora caninum | 72 | species | invertebrates | protozoa | 29176 |
| neotestudina rosatii | 2 | species | plants | fungi | 160030 |
| new york virus | 7 | species | viruses | viruses | 44755 |
| newcastle disease virus | 93 | species | viruses | viruses | 11176 |
| nigrospora sphaerica | 9 | species | plants | fungi | 114231 |
| nipah virus | 51 | species | viruses | viruses | 121791 |
| nocardia | 83 | genus | bacteria | | 1817 |
| nocardia asteroides | 51 | species | bacteria | bacteria | 1824 |
| nocardia brasiliensis | 26 | species | bacteria | bacteria | 37326 |
| nocardia farcinica | 23 | species | bacteria | bacteria | 37329 |
| nocardia nova | 13 | species | bacteria | bacteria | 37330 |
| nocardia otitidiscaviarum | 17 | species | bacteria | bacteria | 1823 |
| nocardia pseudobrasiliensis | 8 | species | bacteria | bacteria | 45979 |
| nocardia transvalensis | 10 | species | bacteria | bacteria | 37333 |
| nocardiopsis | 26 | genus | bacteria | | 2013 |
| norovirus | 69 | genus | viruses | | 142786 |
| norovirus gi | 1 | no rank | viruses | viruses | 122928 |
| norwalk virus | 73 | species | viruses | viruses | 11983 |
| norwalk-like virus | 49 | no rank | viruses | viruses | 95340 |
| nosema africanum | -3 | species | | fungi | |
| nosema apis | 22 | species | plants | fungi | 35231 |
| nosema branchialis | -3 | species | | fungi | |
| nosema ceylonensis | -3 | species | | fungi | |
| nosema connori | 4 | species | | fungi | |
| nosema lophi | -3 | species | | fungi | |
| nosema ocularum | 1 | species | | fungi | |
| notocotylus attenuatus | 8 | species | invertebrates | helminths | 138570 |
| notocotylus impricatus | -3 | species | | helminths | |
| notocotylus thienemanni | -3 | species | | helminths | |
| notoedres cati | 8 | species | invertebrates | | 124612 |
| notoedres douglasi | 1 | species | | | |
| notoedres muris | 1 | species | | | |
| notoedres oudemansi | 1 | species | | | |
| novirhabdovirus | 15 | genus | viruses | | 186778 |
| nupapillomavirus | -3 | genus | viruses | | 475861 |
| nyando virus | 1 | no rank | viruses | viruses | 35316 |
| oceanospirillum | 21 | genus | bacteria | | 965 |