d-amino acids signal a stress-dependent run-away response in Vibrio cholerae
Oihane Irazoki, Josy ter Beek, Laura Álvarez, André Mateus, Rémy Colin, Athanasios Typas, Mikhail M. Savitski, Victor Sourjik, Ronnie P.‐A. Berntsson, Felipe Cava
Abstract
Abstract To explore favourable niches while avoiding threats, many bacteria use a chemotaxis navigation system. Despite decades of studies on chemotaxis, most signals and sensory proteins are still unknown. Many bacterial species release d -amino acids to the environment; however, their function remains largely unrecognized. Here we reveal that d -arginine and d -lysine are chemotactic repellent signals for the cholera pathogen Vibrio cholerae . These d -amino acids are sensed by a single chemoreceptor MCP DRK co-transcribed with the racemase enzyme that synthesizes them under the control of the stress-response sigma factor RpoS. Structural characterization of this chemoreceptor bound to either d -arginine or d -lysine allowed us to pinpoint the residues defining its specificity. Interestingly, the specificity for these d -amino acids appears to be restricted to those MCP DRK orthologues transcriptionally linked to the racemase. Our results suggest that d -amino acids can shape the biodiversity and structure of complex microbial communities under adverse conditions.