| Origin | Code | Comment | Supplementary Taxo |
| Xanthobacter autotrophicus | ISXau | | |
| Xanthomonadales bacterium | ISXba | | |
| Xanthomonas axonopodis | ISXax | | |
| Xanthomonas campestris | ISXca | | |
| Xanthomonas citri | ISXci | | |
| Xanthomonas fuscans | ISXfu | | |
| Xanthomonas oryzae | ISXo | Predefined common nomenclature | |
| Xanthomonas translucens | ISXtr | | |
| Xenorhabdus bovienii | ISXbo | | |
| Xenorhabdus nematophila | ISXne | | |
| Xenorhabdus poinarii | ISXpo | | |
| Xenorhabdus sp. | ISXsp | | |
| Xylella fastidiosa | ISXfa | | |