Including our newly discovered 14 amino acid conjugation, BA conjugates derived from 20 common amino acid conjugation mediated by gut microbiota were revealed . These findings suggested that gut microbiota could universally mediate the amidation of AAs and free BAs. Notably, most of the AA-BAs detected from human and mouse feces belonged to trihydroxy C24 BA conjugates and dihydroxy C24 BA conjugates (Figure and C, violet and blue boxes), which might be due to the high abundance of their free forms in feces. The dioxoHDCA/dioxoCDCA conjugates were detected only from mouse feces, whereas the isoLCA conjugates were detected only from human feces (Table ), which was consistent with the previous report that isoLCA is the major BA from human feces . The above results implied that the amidation mediated by gut microbiota might not be limited to AA and BA, and other small molecules that could be amidated with BAs might also participate in the synthesis of BA conjugates under the mediation of gut microbiota.