- Genus Undibacterium
- Undibacterium sp
- CECT 7724
- Undibacterium sp
- Genus Urechidicola
- Urechidicola sp, Shin and Yi 2020
- CECT 30802 T; CCM 9340
- Urechidicola sp, Shin and Yi 2020
- Genus Uruburuella
- Uruburuella suis, Vela et al. 2005
- CECT 5685 T; CCUG 47806
- Uruburuella suis, Vela et al. 2005
- Genus Usitatibacter
- Usitatibacter palustris, Vieira et al. 2021
- CECT 9242 T; DSM 104440; LMG 29997
- Usitatibacter rugosus, Vieira et al. 2021
- CECT 9241 T; DSM 104443; LMG 29998
- Usitatibacter palustris, Vieira et al. 2021