The LuxS/AI-2 quorum sensing system regulates osmotic adaptation, motility, and type VI secretion system in Halomonas...

As a widespread quorum sensing (QS) system in bacteria, the LuxS/AI-2 QS system can coordinate bacterial group behaviors to adapt to diverse environments. However, its roles in halophiles remain largely unexplored. Here, we report that the AI-2 activity of Halomonas elongata, a moderately halophilic bacterium, is closely associated with environmental salinity. Moreover, luxS deletion abolishes AI-2 production and impairs the growth of H. elongata at various salt concentrations. Transcriptomic and qRT-PCR analyses revealed that the LuxS/AI-2 QS system regulates the transcription of the compatible solute ectoine degradation genes doeCD, thereby modulating intracellular ectoine levels to facilitate osmotic adaptation. Furthermore, the LuxS/AI-2 QS system is also involved in motility and the type VI secretion system (T6SS) in H. elongata. This work provides new insights into the regulatory mechanism of LuxS/AI-2 QS system underlying osmoadaptation in halophiles.