The RNA Chaperone Hfq Impacts Growth, Metabolism and Production of Virulence Factors in Yersinia enterocolitica

Abstract

To adapt to changes in environmental conditions, bacteria regulate their gene expression at the transcriptional but also at the post-transcriptional level, e.g. by small RNAs (sRNAs) which modulate mRNA stability and translation. The conserved RNA chaperone Hfq mediates the interaction of many sRNAs with their target mRNAs, thereby playing a global role in fine-tuning protein production.In this study, we investigated the significance of Hfq for the enteropathogen Yersina enterocolitica serotype O:8. Hfq facilitated optimal growth in complex and minimal media. Our comparative protein analysis of parental and hfq-negative strains suggested that Hfq promotes lipid metabolism and transport, cell redox homeostasis, mRNA translation and ATP synthesis, and negatively affects carbon and nitrogen metabolism, transport of siderophore and peptides and tRNA synthesis. Accordingly, biochemical tests indicated that Hfq represses ornithine decarboxylase activity, indole production and utilization of glucose, mannitol, inositol and 1,2-propanediol. Moreover, Hfq repressed production of the siderophore yersiniabactin and its outer membrane receptor FyuA. In contrast, hfq mutants exhibited reduced urease production. Finally, strains lacking hfq were more susceptible to acidic pH and oxidative stress. Unlike previous reports in other Gram-negative bacteria, Hfq was dispensable for type III secretion encoded by the virulence plasmid.Using a chromosomally encoded FLAG-tagged Hfq, we observed increased production of Hfq-FLAG in late exponential and stationary phases. Overall, Hfq has a profound effect on metabolism, resistance to stress and modulates the production of two virulence factors in Y. enterocolitica, namely urease and yersiniabactin.

Genome-Wide Analysis of Small RNAs Expressed by Yersinia pestis Identifies a Regulator of the Yop-Ysc Type III Secretion System

“…Geng et al speculated that Hfq participates in the repression of this system under certain conditions (30); however, our study illustrates that the T3SS of Y. pestis is activated in an Hfq-dependent manner under the conditions examined here. Interestingly, the loss of Hfq does not influence the synthesis of pYV-encoded T3SS proteins in Y. enterocolitica, suggesting differences in the Hfq-dependent posttranscriptional control of virulence determinants among Yersinia species (52).…”

Small RNAs in Bacteria and Archaea

“…It is structurally related to eukaryotic/archaeal (heteroheptameric) Sm/Lsm proteins with which it shares an Sm-motif involved in RNA binding (Mura, Randolph, Patterson, & Cozen, 2013). Deletion of hfq in enterobacteria gives strong pleiotropic phenotypes (abolished virulence, impaired stress responses, growth defects) (Kakoschke et al, 2014;, reflecting its central role in sRNA-mediated regulation (Link, Valentin-Hansen, & Brennan, 2009;Vogel & Luisi, 2011). Most enterobacterial trans-encoded sRNAs require the RNA chaperone Hfq for regulatory activity.…”

Post-transcriptional regulation of type III secretion in plant and animal pathogens

“…Whereas Hfq is dispensable for T3SS production in Y. enterocolitica [34,35], Hfq positively regulates T3SS in Y. pseudotuberculosis and Y. pestis . LcrF is the AraC/XylS activator of T3SS in Y. pestis .…”