Systematic analysis of cyclic di‐GMP signalling enzymes and their role in biofilm formation and virulence in Yersinia pestis

Abstract

Summary: Cyclic di‐GMP (c‐di‐GMP) is a signalling molecule that governs the transition between planktonic and biofilm states. Previously, we showed that the diguanylate cyclase HmsT and the putative c‐di‐GMP phosphodiesterase HmsP inversely regulate biofilm formation through control of HmsHFRS‐dependent poly‐β‐1,6‐N‐acetylglucosamine synthesis. Here, we systematically examine the functionality of the genes encoding putative c‐di‐GMP metabolic enzymes in Yersinia pestis . We determine that, in addition to hmsT and hmsP , only the gene y3730 encodes a functional enzyme capable of synthesizing c‐di‐GMP. The seven remaining genes are pseudogenes or encode proteins that do not function catalytically or are not expressed. Furthermore, we show that HmsP has c‐di‐GMP‐specific phosphodiesterase activity. We report that a mutant incapable of c‐di‐GMP synthesis is unaffected in virulence in plague mouse models. Conversely, an hmsP mutant, unable to degrade c‐di‐GMP, is defective in virulence by a subcutaneous route of infection due to poly‐β‐1,6‐N‐acetylglucosamine overproduction. This suggests that c‐di‐GMP signalling is not only dispensable but deleterious for Y. pestis virulence. Our results show that a key event in the evolution of Y. pestis from the ancestral Yersinia pseudotuberculosis was a significant reduction in the complexity of its c‐di‐GMP signalling network likely resulting from the different disease cycles of these human pathogens.