Manipulation of the Quorum Sensing Signal AI-2 Affects the Antibiotic-Treated Gut Microbiota

The mammalian gut microbiota harbors a diverse ecosystem where hundreds of bacterial species interact with each other and their host. Given that bacteria use signals to communicate and regulate group behaviors (quorum sensing), we asked whether such communication between different commensal species can influence the interactions occurring in this environment. We engineered the enteric bacterium, Escherichia coli, to manipulate the levels of the interspecies quorum sensing signal, autoinducer-2 (AI-2), in the mouse intestine and investigated the effect upon antibiotic-induced gut microbiota dysbiosis. E. coli that increased intestinal AI-2 levels altered the composition of the antibiotic-treated gut microbiota, favoring the expansion of the Firmicutes phylum. This significantly increased the Firmicutes/Bacteroidetes ratio, to oppose the strong effect of the antibiotic, which had almost cleared the Firmicutes. This demonstrates that AI-2 levels influence the abundance of the major phyla of the gut microbiota, the balance of which is known to influence human health. [Display omitted] •Streptomycin almost clears Firmicutes as Bacteroidetes dominate the gut microbiota•Engineered Escherichia coli manipulate AI-2 levels in the mouse gut•AI-2 produced by E. coli favors the Firmicutes while hindering the Bacteroidetes•AI-2 can shape the microbiota composition under conditions of dysbiosis The balance between the Bacteroidetes and Firmicutes phyla in the gut bacterial community influences host health. Thompson et al. investigate the impact of the interspecies signal autoinducer-2 on this balance. Despite the streptomycin-induced dominance of the microbiota by the Bacteroidetes, increased AI-2 counteracts antibiotic-induced dysbiosis and favors Firmicutes.