The Mannose Phosphotransferase System in <i>Enterococcus lactis</i> Is Essential for Gastrointestinal Colonization

Enterococcus lactis, a recently established species that was previously classified as Enterococcus faecium clade B, is a common commensal in human and animal intestines. Unlike the opportunistic pathogen E. faecium , it is largely harmless and rarely associated with clinical infections. Given its recent taxonomic classification, studies on this bacterium are scarce, and the key mechanisms that facilitate its intestinal colonization remain particularly elusive. The capability to utilize different sugars is an important factor in colonizing different ecological niches, particularly in the Gastrointestinal (GI) tract, where carbohydrates are fiercely competed for by a large number of microbes. In this study, we characterized an E. lactis pts gene cluster that is highly conserved in E. lactis and E. faecium , and is widely present in numerous other bacterial species. Two gene-deletion mutants of the putative pts gene cluster exhibited markedly reduced growth on mannose and failed to colonize the GI tract of mice. These results demonstrate the crucial role of the mannose-utilization PTS in the intestinal colonization of E. lactis , providing new insight into the carbohydrate-driven colonization mechanisms of gut microbes.