Enterocloster citroniae and related gut microbiome species modulate Vibrio cholerae biofilm formation through the production of bioactive small molecules
Cholera is a deadly diarrheal disease that affects millions of people globally. Although V. cholerae, the causative agent of the disease, has been extensively studied in isolation, it was relatively recently that scientists started investigating its interactions with the gut microbiota. Our group and others previously showed that microbiota-derived metabolites significantly influence V. cholerae behavior. By investigating how an organic extract of human feces affects V. cholerae gene expression, we recently showed that gut metabolites strongly suppress swimming motility, a virulence factor important for host colonization. Interestingly, extracts of pure cultures of a single gut commensal, Enterocloster citroniae, recapitulated this inhibitory effect. Here, we present a comprehensive examination of the effect of small molecules produced by E. citroniae and related species on V. cholerae behavior. We show that E. citroniae small molecules inhibit motility by various V. cholerae strains. We also show that several phylogenetically related species produce this activity, although the magnitude of the effect varies between strains. Using biofilm formation assays in static and shear flow conditions, we show that V. cholerae strongly induces biofilm formation in response to E. citroniae metabolites. Transcriptome and reporter analyses show that several genes involved in the synthesis of an extracellular polysaccharide are induced by growth in the presence of E. citroniae metabolites. Lastly, we show that V. cholerae interactions with host epithelial cells are also modulated by compounds produced by this commensal. These findings advance our understanding of microbiome-pathogen interactions and how commensal bacteria influence V. cholerae virulence through the production of small molecules. In the future, this knowledge may be used to design novel microbiome-based therapeutic approaches to combat cholera and other infections. Overall design: RNA-seq profiles of Vibrio cholerae C6706 grown in the absence or presence of an organic extract of Enterocloster citroniae WAL17108 cultures.