**5. Conclusions**

Sulfate-reducing bacteria are present in various environments and they make a high impact on animal and human health since their presence is a possible contributing factor in the development of inflammatory bowel diseases. Their morphology (vibrio, spiral, rods, and cocci) and diversity are highly influenced by environmental conditions including temperature, pH, oxygen presence and

substrate availability. Unique in nature is anaerobic sulfate-reducing bacteria metabolism in which hydrogen sulfide is produced in the process of electron acceptors (mainly sulfate ions) reduction (the process of dissimilatory sulfate reduction). The study clearly showed that mixed SRB cultures obtained from healthy and with ulcerative mice were equally polymorphic (the most often vibrio and coccus shape occurred). Though, the production of hydrogen sulfide differs significantly among isolated cultures. It was observed that isolates from not healthy mice produced higher hydrogen sulfide amounts. This observation is emphasizing correlations between intestine inflammation occurrence and hydrogen sulfide concentrations. The meta-analysis confirmed these correlations. Presently, it is still not fully understood the occurrence processes of inflammatory bowel diseases, including ulcerative colitis. Though, the study is emphasizing one more time that the occurrence of SRB in the samples with developed IBD is pointing out the importance of issues concerning sulfate-reducing bacteria.

**Author Contributions:** Conceptualization, I.K., O.L., and D.D.; methodology, I.K., O.L., and M.V.; validation, S.J., M.V., and D.D.; formal analysis, S.J., M.V., and L.D.; investigation, O.L., I.K.; resources, I.K.; data curation, L.B., D.D.; writing—original draft preparation, I.K., D.D., S.J., and M.V.; writing—review and editing, I.K., J.H., L.B., and L.D.; visualization, I.K.; supervision, M.V.; project administration, I.K.; funding acquisition, I.K., D.D., and M.V.

**Funding:** This research was supported by Grant Agency of the Masaryk University (MUNI/A/0902/2018).

**Conflicts of Interest:** The authors declare no conflict of interest.
