Crosstalk between cyclic-di-guanosine monophosphate and the sensor kinase MtrB regulates MtrA-dependent genes, bacterial growth, biofilm formation and lysosomal trafficking of .

Cyclic-di-guanosine monophosphate (c-di-GMP) plays an important role in bacterial signalling networks. C-di-GMP exerts a regulatory function through binding to diverse molecules that include transcription factors, riboswitches and sensor kinases (SKs), thereby regulating diverse processes. Here, we demonstrate the crosstalk between c-di-GMP and the SK MtrB of . MtrB phosphorylates and regulates its cognate response regulator MtrA. C-di-GMP binds directly to the cytosolic domain of MtrB to inhibit its autophosphorylation. C-di-GMP levels in were manipulated by overexpressing a c-di-GMP synthesizing enzyme and a degrading enzyme . We demonstrate that overexpression of lowers growth of the bacterium both and in grown in macrophages. This is in conformity with lowered expression of and selected genes of the regulon involved in cell wall turnover in the -overexpressing strain compared to the parent strain. We also demonstrate that overexpression of in hinders biofilm formation, whereas overexpression of has the opposite effect. Neither of the two genes could rescue the biofilm defective phenotype of the MtrB knock out mutant (), suggesting that c-di-GMP exerts its role on biofilm formation through MtrB. Finally, we show by fluorescence microscopy that the trafficking of overexpressing is significantly higher than that of the parent strain and that this is linked to reduced expression of the MtrB-dependent genes and , which play a role in subversion of lysosomal trafficking of . These results provide important new insight into the crosstalk between c-di-GMP and MtrB in .