| Iamia majanohamensis | NBRC 102561T |
| Idiomarina halophila | NBRC 109833T |
| Idiomarina homiensis | NBRC 106395T |
| Idiomarina piscisalsi | NBRC 108617T |
| Idiomarina sediminum | NBRC 109488T |
| Idriella fertilis | NBRC 30445 |
| Idriella lunata | NBRC 7700T, NBRC 32041, NBRC 100566 |
| Ignatzschineria cameli | NBRC 113042T |
| Ignavibacterium album | NBRC 101810T |
| Ilumatobacter coccineus | NBRC 103263T |
| Ilumatobacter nonamiensis | NBRC 109120T |
| Ilyomonas limi | NBRC 112826T |
| Incrucipulum capitatum | NBRC 113938 |
| Incrucipulum ciliare | NBRC 113861, NBRC 113940, NBRC 113941 |
| Incrucipulum foliicola | NBRC 113942T |
| Incrucipulum radiatum | NBRC 113862, NBRC 113933 |
| Infundibulicybe gibba | NBRC 100092 |
| Inhella inkyongensis | NBRC 103252T |
| Inonotus cuticularis | NBRC 9788 |
| Inonotus dryadeus | NBRC 9352 |
| Inonotus mikadoi | NBRC 6517 |
| Inonotus obliquus | NBRC 113406, NBRC 113407, NBRC 113408, NBRC 113409, NBRC 114701, NBRC 114702 |
| Insolitispirillum peregrinum subsp. integrum | NBRC 13617T |
| Insolitispirillum peregrinum subsp. peregrinum | NBRC 14922T |
| Interfilum sp. (class: Ulvophyceae) | NBRC 113306 |
| Intestinibaculum porci | NBRC 113396T |
| Intrasporangium calvum | NBRC 12989T |
| Intrasporangium chromatireducens | NBRC 113233T |
| Intrasporangium flavum | NBRC 110749T |
| Intrasporangium oryzae | NBRC 101802T |
| Intrasporangium sp. | NBRC 106350, NBRC 106456, NBRC 106457, NBRC 107105, NBRC 116604 |
| Involutiscutellula rubra | NBRC 9271, NBRC 9272, NBRC 9273T, NBRC 9274, NBRC 9275, NBRC 9276, NBRC 9277, NBRC 9371 |
| Iodobacter fluviatilis | NBRC 102505T |
| Iodophanus carneus | NBRC 7799, NBRC 7800, NBRC 7801 |
| Irpex lacteus | NBRC 5367, NBRC 106829 |
| Isaria cateniannulata | NBRC 109997 |
| Isaria cicadae | NBRC 33061, NBRC 33259 |
| Isaria nipponica | NBRC 108996 |
| Isaria sp. | NBRC 103708, NBRC 103709, NBRC 104353 |
| Isochrysis galbana (class: Haptophyceae) | NBRC 102813 |
| Isochrysis sp. (class: Haptophyceae) | NBRC 102814, NBRC 102815, NBRC 102941 |
| Isoptericola halotolerans | NBRC 104116T |
| Isoptericola hypogeus | NBRC 104396T |
| Isoptericola jiangsuensis | NBRC 106522 |
| Isoptericola sp. | NBRC 110988, NBRC 110993, NBRC 110999, NBRC 111000, NBRC 111001 |
| Isoptericola variabilis | NBRC 104115T |
| Issatchenkia occidentalis | NBRC 1904T, NBRC 105118, NBRC 105120, NBRC 105179 |
| Issatchenkia orientalis | NBRC 1279T, NBRC 105119, NBRC 105121, NBRC 105122, NBRC 105123 |
| Issatchenkia scutulata var. exigua | NBRC 1896T, NBRC 10077, NBRC 10078 |
| Issatchenkia scutulata var. scutulata | NBRC 1895T |
| Issatchenkia sp. | NBRC 10049, NBRC 10050, NBRC 10051, NBRC 10068, NBRC 10069, NBRC 10070, NBRC 10079, NBRC 10080, NBRC 10081, NBRC 10082, NBRC 10083, NBRC 10084, NBRC 10085, NBRC 10086, NBRC 10087, NBRC 10088, NBRC 104879, NBRC 105180 |
| Issatchenkia terricola | NBRC 0933T, NBRC 1798, NBRC 1888, NBRC 1907 |
| Isthmolongispora ampulliformis | NBRC 6787T |
| Isthmolongispora lanceata | NBRC 100994T |
| Isthmolongispora minima | NBRC 30075, NBRC 111160 |
| Isthmolongispora quadricellularis | NBRC 100995 |
| Isthmolongispora variabilis | NBRC 100996 |
| Itersonilia perplexans | NBRC 31349, NBRC 31350, NBRC 31655T |
| Itersonilia pyriformis | NBRC 31656T |
| Ithmotricladia cf. laeensis | NBRC 106796 |
