Autoinducer-2 (AI-2) serves as a quorum-sensing signaling molecule that mediates both intraspecies and interspecies communication among bacteria, and plays critical roles in regulating various bacterial behaviors. In the present study, we investigated the functions of AI-2 signaling in the extremophilic bacterium Deinococcus radiodurans R1 by construction of the LuxS gene disruption mutant, survival phenotype assay and gene transcription assay. The gene mutant (DRΔLuxS), which was unable to produce AI-2, was significantly more sensitive to both gamma radiation and H2O2 compared with the wild-type strain. Addition of the wild-type-derived spent medium into the cell culture of DRΔLuxS fully restored the radioresistance of D. radiodurans. A higher level of reactive oxygen species accumulated in the mutant compared with the wild type under normal or oxidative stress. Quantitative real-time PCR assays showed that transcriptional levels of stress-related proteins, including catalase, extracellular nuclease, Dps-1 and ABC transporters, were decreased in DRΔLuxS, indicating that AI-2 is involved in regulation of stress-related genes of D. radiodurans. Hence, AI-2 signaling may contribute to the extreme resistance of D. radiodurans to radiation and oxidative stresses.
Keywords: Autoinducer-2; Deinococcus radiodurans R1; LuxS; Stress resistance.