Integration of DSF and Temperature Signals for RpfC/RpfG Two-Component System Modulating Protease Production in Stenotrophomonas maltophilia FF11.

Two-component signal system (TCS) is the predominant bacterial sense-and-response machinery. RpfC/RpfG TCS involved in quorum sensing molecule Diffuse Signal Factor (DSF) signal perception and transduction was well studied in many bacteria. However, whether other environmental factors participating in the signal perception and transduction of RpfC/RpfG was still unclear. Here, we showed that RpfC/RpfG could integrate temperature and DSF signal partially controlling the production of the temperature-dependent protease (SmtP) in S. maltophilia FF11, a strain isolated from frozen Antarctic krill, exhibited spoilage potential due to secret more protease at low temperatures involving in protein degradation. qRT-PCR analysis revealed rpf system mediating approximately 60% transcription activity of Clp, a critical transcription factor linking with LotS/LotR, consisting a signal network controlling completely the SmtP production in previous study. Protease production was partially reduced in rpfF (coding DSF synthetase) mutant strains at 15 °C or 25 °C, not be increased through addition DSF or overexpression RpfF in WT at 37 °C, indicating that DSF was effective for protease production only at low temperatures in S. maltophilia. Additionally, biochemical analysis revealed the enzymatic activity of RpfG from strain FF11 cultured at 37 °C or DSF-deficient strains grown at 25 °C was significantly reduced compared to that of RpfG from strain FF11 cultured at 25 °C. These findings outline an interplay mechanism that allows S. maltophilia to integrate quorum sensing and temperature cues controlling protease production, and imply a potential relationship between two distinct systems of RpfC/RpfG and LotS/LotR.