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.
Highlights
The genus Yersinia includes three human pathogenic species, namely Y. pestis, the agent of plague and two enteropathogenic species, Y. pseudotuberculosis and Y. enterocolitica
The cluster of genes flanking hfq is similar to that described in Y. pestis and Y. pseudotuberculosis as well as in E. coli [29,47]
Loss of hfq led to the same phenotypes in both strains, indicating that Hfq plays a conserved role in Y. enterocolitica serotype O:8
Summary
The genus Yersinia includes three human pathogenic species, namely Y. pestis, the agent of plague and two enteropathogenic species, Y. pseudotuberculosis and Y. enterocolitica. Y. enterocolitica virulence factors include proteins important for early stages of infection, such as urease, a multisubunit metalloenzyme which facilitates survival to stomach acidity [3,4] or the outer membrane adhesin called invasin which promotes transcytosis across the epithelial barrier [5]. The HPI encodes proteins involved in production and import of the siderophore yersiniabactin [8]. These proteins include the transcriptional activator YbtA, the biosynthetic enzymes Irp1-Irp and Irp, the inner membrane ABC transporters Irp and Irp, and the yersiniabactin receptor FyuA, which is localized in the outer membrane [8,9,10,11,12,13,14,15]. Yersiniabactin production and utilization is an essential virulence trait for Y. enterocolitica in mouse infection [10,11,16]
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