In case of invE mRNA, a change of the signal that represents thermodynamic alteration of the structure was actually detected in circular

dichroism spectroscopy [34] for the 140 nucleotides selleck products invE RNA [11]. Furthermore, the characteristics of the binding of invE mRNA to Hfq in low-salt (Fig. 5) and low-temperature [11] conditions are consistent with an opening of the secondary structure of the RNA through the binding of multiple Hfq molecules. Of note, the pattern of binding of invE RNA to Hfq in low-salt buffer was remarkably similar to that seen in low temperature conditions [11]. That indicates that the distribution of RNA-Hfq interaction strength upon the ionic circumstance exists in a similar range, which is defined by the thermodynamic distribution of Hfq binding between 30°C and 37°C. To date, specific molecular sensors of low osmotic conditions or mild temperature change have not been identified. Our results suggest that low osmotic conditions evoke a decrease in intracellular ionic strength, resulting in a similar effect on the strength of the RNA-Hfq

interaction as that of decreased temperature. This raises the interesting possibility that post-transcriptional regulation itself represents a sensing LGX818 mouse system for changes in temperature and osmotic pressure. The lack of active translation of invE mRNA could result in its destabilization [24]. In fact, one of the mechanisms of post-transcriptional regulation is the regulation of mRNA stability [35]. The degradosome is a well-characterized mRNA degradation system that consists of RNaseE, as well as Hfq (46). We examined the role of RNaseE in TTSS synthesis using a deletion mutant (Δrne 701–892) of the C-terminal region of RnaseE and E. coli rne-3071 ts strain N3431 [36] carrying expression plasmids for virF, invE and TTSS genes (pJK1143 and pJK1142, respectively) [4]. TTSS synthesis was unaffected in either of the two strains (data not shown), which indicates that an as-yet unidentified degradation pathway involving Hfq likely plays a role in the degradation of invE mRNA. Similar to other bacterial

species, hfq mutants of S. sonnei and S. flexneri exhibited decreased virulence in vivo. If the Megestrol Acetate up-regulation of virulence gene expression due to hfq deletion leads to efficient antigen presentation for the host immune-system, then the hfq deletion is a potentially viable candidate for the development of a more effective Shigella vaccine, one that goes beyond the serotype-specific effects seen in current vaccine development [37]. In fact, a Shigella hfq mutant is currently under Tariquidar research buy evaluation for use as a vaccine in the guinea pig model [38]. Shigella can survive in a range of environmental conditions, such as low osmotic pressure and low temperature, where strict repression of virulence gene expression is required. The development of a bi-functional sensing system for osmolarity and temperature represents an important adaptation for survival by this organism.