Hfq-dependent, co-ordinate control of cyclic diguanylate synthesis and catabolism in the plague pathogen Yersinia pestis.

Yersinia pestis, the cause of the disease plague, forms biofilms to enhance flea-to-mammal transmission. Biofilm formation is dependent on exopolysaccharide synthesis and is controlled by the intracellular levels of the second messenger molecule cyclic diguanylate (c-di-GMP), but the mechanisms by which Y. pestis regulates c-di-GMP synthesis and turnover are not fully understood. Here we show that the small RNA chaperone Hfq contributes to the regulation of c-di-GMP levels and biofilm formation by modulating the abundance of both the c-di-GMP phosphodiesterase HmsP and the diguanylate cyclase HmsT. To do so, Hfq co-ordinately promotes hmsP mRNA accumulation while simultaneously decreasing the stability of the hmsT transcript. Hfq-dependent regulation of HmsP occurs at the transcriptional level while the regulation of HmsT is post-transcriptional and is localized to the 5' untranslated region/proximal coding sequence of the hmsT transcript. Decoupling HmsP from Hfq-based regulation is sufficient to overcome the effects of Δhfq on c-di-GMP and biofilm formation. We propose that Y. pestis utilizes Hfq to link c-di-GMP levels to environmental conditions and that the disregulation of c-di-GMP turnover in the absence of Hfq may contribute to the severe attenuation of Y. pestis lacking this RNA chaperone in animal models of plague.

Bellows LE ，Koestler BJ ，Karaba SM ，Waters CM ，Lathem WW ... -  《-》

CsrA Enhances Cyclic-di-GMP Biosynthesis and Yersinia pestis Biofilm Blockage of the Flea Foregut by Alleviating Hfq-Dependent Repression of the hmsT mRNA.

Silva-Rohwer AR ，Held K ，Sagawa J ，Fernandez NL ，Waters CM ，Vadyvaloo V ... -  《mBio》

Differential control of Yersinia pestis biofilm formation in vitro and in the flea vector by two c-di-GMP diguanylate cyclases.

Sun YC ，Koumoutsi A ，Jarrett C ，Lawrence K ，Gherardini FC ，Darby C ，Hinnebusch BJ ... -  《PLoS One》

The hmsT 3' untranslated region mediates c-di-GMP metabolism and biofilm formation in Yersinia pestis.

Yersinia pestis, the cause of plague, forms a biofilm in the proventriculus of its flea vector to enhance transmission. Biofilm formation in Y. pestis is regulated by the intracellular levels of cyclic diguanylate (c-di-GMP). In this study, we investigated the role of the 3' untranslated region (3'UTR) in hmsT mRNA, a transcript that encodes a diguanylate cyclase that stimulates biofilm formation in Y. pestis by synthesizing the second messenger c-di-GMP. Deletion of the 3'UTR increased the half-life of hmsT mRNA, thereby upregulating c-di-GMP levels and biofilm formation. Our findings indicate that multiple regulatory sequences might be present in the hmsT 3'UTR that function together to mediate mRNA turnover. We also found that polynucleotide phosphorylase is partially responsible for hmsT 3'UTR-mediated mRNA decay. In addition, the hmsT 3'UTR strongly repressed gene expression at 37°C and 26°C, but affected gene expression only slightly at 21°C. Our findings suggest that the 3'UTR might be involved in precise and rapid regulation of hmsT expression, allowing Y. pestis to fine-tune c-di-GMP synthesis and consequently regulate biofilm production to adapt to the changing host environment.

Zhu H ，Mao XJ ，Guo XP ，Sun YC ... -  《-》

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

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.

Bobrov AG ，Kirillina O ，Ryjenkov DA ，Waters CM ，Price PA ，Fetherston JD ，Mack D ，Goldman WE ，Gomelsky M ，Perry RD ... -  《-》