Global identifiction of virulence-associated small non-coding RNAs in Yersinia pseudotuberculosis

Lately, it has been demonstrated that small non-coding RNAs (sRNAs) play a crucial role in virulence gene regulation in several bacterial species. A recent study demonstrated that the sRNA chaperone Hfq is required for full virulence of the enteropathogenic bacterium Yersinia pseudotuberculosis and the closely related plague bacterium, Y. pestis (1). These data indicate that sRNAs are also critical for Yersinia virulence. In fact, we found that in Y. pseudotuberculosis the post-transciptional Csr system participates in motility, stress resistance and the regulation of the global virulence regulator RovA. RovA controls the expression of early stage virulence genes, which are important for Y. pseudotuberculosis to colonize and penetrate the intestinal tract (2). Using a deep sequencing analysis, we initiated a global approach to identify and characterize further virulence-associated sRNAs in Y. pseudotuberculosis. Sequencing of RNA libraries from Y. pseudotuberculosis wildtype and an hfq mutant grown either at 25°C to stationary phase (simulating environmental conditions/early infection phase) or at 37°C to exponential phase (late infection phase) led to the identification of 315 putative ncRNA out of which 15 were encoded on the Yersinia virulence plasmid pYV. The majority of these newly identified sRNAs were only found in pathogenic Yersiniae. According to the 454 data, one out of four is temperature-regulated and around 40% are Hfq-dependent. Expression of selected candidates was further analysed and their influence on virulence investigated.