| Origin | Code | Comment | Supplementary Taxo |
|---|
| Tagabacteria bacterium | ISTaba | | Candidatus Tagabacteria bacterium |
| Tannerella forsythia | ISTfo | | |
| Terrabacter sp. | ISTesp | | |
| Terrabacteria group bacterium | ISTgr | | |
| Tetragenococcus halophilus | ISTeha | | |
| Thalassiobium sp. | ISTasp | | |
| Thalassobaculum litoreum | ISThli | | |
| Thalassobius mediterraneus | ISTme | | |
| Thalassospira sp. | ISThasp | | |
| Thauera humireducens | ISThu | | |
| Thauera phenylacetica | ISThph | | |
| Thauera sp. | ISTha | | |
| Thaumarchaeota archaeon | ISThar | | |
| Thermacetogenium phaeum | ISTph | | |
| Thermaerobacter subterraneus | ISTsu | | |
| Thermoanaerobacter ethanolicus | ISTet | | |
| Thermoanaerobacter kivui | ISTki | | |
| Thermoanaerobacter pseudethanolicus | ISTps | | |
| Thermoanaerobacter sp. | ISTsp | | |
| Thermoanaerobacter tengcongensis | ISTte | | |
| Thermoanaerobacter wiegelii | ISTwi | | |
| Thermoanaerobacterales bacterium | ISThba | | |
| Thermoanaerobacterium thermosaccharolyticum | ISThth | | |
| Thermoanaerobacterium xylanolyticum | ISTxy | | |
| Thermobacillus composti | ISTco | | |
| Thermobacillus sp. | ISTrsp | | |
| Thermobifida fusca | ISTfu | | |
| Thermococcus kodakarensis | ISTko | | |
| Thermococcus litoralis | ISTli | | |
| Thermococcus sibiricus | ISTsi | | |
| Thermodesulfobium narugense | ISTna | | |
| Thermomonas hydrothermalis | ISThy | | |
| Thermophilic bacterium | ISTba | | |
| Thermoplasma acidophilum | ISTac | | |
| Thermoplasma volcanium | ISTvo | | |
| Thermoplasmatales archaeon | ISTar | | |
| Thermosynechococcus elongatus | ISTel | | |
| Thermotoga maritima | ISTma | | |
| Thermus aquaticus | ISTaq | | |
| Thermus thermophilus | ISTth | | |
| Thioalkalivibrio nitratireducens | ISTni | | |
| Thioalkalivibrio sp | ISThi | | |
| Thiobacillus denitrificans | ISThde | | |
| Thiobacillus ferrooxidans | ISTfe | | |
| Thiocapsa marina | ISThma | | |
| Thiocapsa roseopersicina | ISTro | | |
| Thiocapsa sp. | ISTisp | | |
| Thiocystis violascens | ISTvi | | |
| Thiomargarita nelsonii | ISTne | | |
| Thiomonas arsenitoxydans | ISTars | | |
| Thiomonas intermedia | ISTin | | |
| Thiomonas sp. | ISThsp | | |
| Thiorhodococcus drewsii | ISTdr | | |
| Thiorhodospira sibirica | ISThsi | | |
| Thiorhodovibrio sp. | ISThio | | |
| Thiothrix nivea | ISThni | | |
| Tistlia consotensis | ISTico | | |
| Tolypothrix campylonemoides | ISTca | | |
| Tolypothrix sp | ISTosp | | |
| Treponema denticola | ISTde | | |
| Trichodesmium erythraeum | ISTer | | |
| Trichormus variabilis | ISTva | | |
| Turicibacter sp. | ISTusp | | |