The Research On The Function Of Shigella Flexneri 2a Hns Gene

When Shigella flexneri 2a 2457T is cultured at 30℃, it's phenotypically avirulent; when grown at 37℃, its virulence improves greately. There is clear evidence that the temperature-dependent expression of the virulence genes is controlled by H-NS protein. H-NS. one of the main nucleoid-associated proteins, is widespread in Gram-negative bacteria. The molecular pathogenic mechanism will be deeply understood with the study of H-NS. This work might lead to develop many better methods or means of preventing and controlling dysenteric diarrhea.To elucidate the role of H-NS protein in bacterial physiology, the hns gene insertion and deletion mutants were constructed with RecA and Red recombination system. Then, growth curve and invasion ability of wild strain and deletion mutant were studied. The result showed that growth velocity of Shigella flexneri 2a 2457T Δ hns was lower than wild strain; Competitive index assay indicated that hns gene is relative to Shigella species invasion.The two-dimensional protein patterns were compared between H-NS-deficient and wild-type strains of Shigella flexneri 2a 2457T. The data showed that expressions of 113 proteins were significantly altered in H-NS-deficient strains. Total of 84 spots were identified by mass spectrum assay, 47 genes of them were up-regulated and 42 were down-regulated. These proteins are not only involved in amino acid biosynthesis, central intermediary and energy metabolism, but also involved in bacterial adaptation to changes in enciromental conditions. In.particular, genes involving in histidine biosynthesis (hisJ, hisG, hisF, hisH, hisB and hisD) were significantly repressed in mutant strain, while other5 genes such as fur-, ftn-, dps, yecl and bcp which related to iron homeostasis were up-regulated. In addition, after hns gene was knock-out, expression of sjh but not stpA, which encodes H-NS paralogues, increased significantly. Based on the results of gene expression alterations, the role of H-NS protein in bacteria physiology could be greatly and deeply understood. Moreover. These results would be helpful for future research on pathogenicity of Shigella spp.