Quorum sensing regulation by the nitrogen phosphotransferase system in .

UNLABELLED

In the opportunistic pathogen , the nitrogen-related phosphotransferase system (PTS) influences multiple virulence behaviors. The PTS is comprised of three enzymes: first PtsP, then the PtsO phosphocarrier, and the final PtsN phosphoacceptor. We previously showed that inactivation enhances LasI-LasR quorum sensing, a system by which regulates genes in response to population density. LasI synthesizes a diffusible autoinducer that binds and activates the LasR receptor, which activates a feedback loop by increasing expression. In this study, we examined the impact of the PTS on quorum sensing. Disruption of increased the expression of some, but not all, tested quorum-controlled genes, including (pyocyanin biosynthesis), (hydrogen cyanide biosynthesis), and, to a lesser extent, (quorum sensing regulator). Expression of these genes remained dependent on LasR and the autoinducer, whether provided endogenously or exogenously. Increased expression in ∆ (or ∆) cells was partly due to the presence of unphosphorylated PtsN, which alone was sufficient to elevate expression. However, we observed residual increases in ∆ or ∆ cells even in the absence of PtsN, suggesting that PtsP and PtsO can regulate gene expression independently of PtsN. Indeed, genetically disrupting the PtsO phosphorylation site impacted gene expression in the absence of PtsN, and transcriptomic evidence suggested that PtsO and PtsN have distinct regulons. Our results expand our view of how the PTS components function both within and apart from the classic phosphorylation cascade to regulate key virulence behaviors in .

IMPORTANCE

often causes severe and difficult-to-treat infections. virulence requires the nitrogen-related phosphotransferase system (PTS), which comprises the phosphocarrier proteins PtsP and PtsO and the final phosphoacceptor, PtsN. The PTS is known to modulate quorum sensing, but little is known about the mechanism of regulation. Here, we examined quorum sensing regulation by the PTS. We showed that the PTS increases quorum sensing-mediated activation of certain genes through the additive effects of both PtsO and PtsN. We also used transcriptomics to determine the regulons of PtsO and PtsN and found that they are largely nonoverlapping. The results position PtsO and PtsN as independent effectors in the PTS and shed new light on virulence regulation in this important pathogen.