d-amino acids signal a stress-dependent run-away response in Vibrio cholerae

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 MCPDRK 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 MCPDRK 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. d-arginine and d-lysine are chemorepellent molecules sensed by a novel chemotaxis receptor in Vibrio cholerae that trigger a run-away response under adverse conditions.

Automated summary

To explore suitable habitats and avoid dangers, many bacteria use a chemotaxis navigation system. However, the signals and sensory proteins involved in chemotaxis are still largely unknown. This study shows that d-arginine and d-lysine act as chemotactic repellent signals for Vibrio cholerae, and that a specific chemoreceptor MCPDRK senses these d-amino acids. The results suggest that d-amino acids can play a role in shaping microbial communities under adverse conditions. Rating: 9/10.