The Society for Antibacterial and Antifungal AgentsActa Medica Okayama134248152042015Role of the Histone-Like Nucleoid Structuring Protein (H-NS) in the Regulation of Virulence Factor Expression and Stress Response in Vibrio vulnificus263274ENAbdelazizElgamlGraduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama UniversityShin-ichiMiyoshiGraduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Temperature is one of the important parameters regulating the expression of virulence factors in bacteria. The global regulator, a histone-like nucleoid structuring protein (H-NS), is known to play a crucial role in this regulation. In the present study, we first clarified the role of H-NS in the temperature-dependent regulation of virulence factor production in Vibrio vulnificus, including that of the cytolytic toxin (V. vulnificus hemolysin: VVH) and the proteolytic enzyme (V. vulnificus protease: VVP). The expression of hns itself was subjected to temperature regulation, where hns was expressed more at 26℃ than at 37℃. VVH production and the expression of its gene vvhA were increased by disruption of the hns gene. H-NS appeared to affect the vvhA expression by the well-documented transcriptional silencing mechanism. On the other hand, hns disruption resulted in the reduction of VVP production and the expression of its gene vvpE. H-NS was suggested to positively regulate vvpE expression through the increase in the level of the rpoS mRNA. Moreover, H-NS was found to contribute to the survival of V. vulnificus in stressful environments. When compared to the wild type strain, the hns mutant exhibited reduced survival rates when subjected to acidic pH, hyperosmotic and oxidative stress.No potential conflict of interest relevant to this article was reported.The Society for Antibacterial and Antifungal AgentsActa Medica Okayama134248152032015Presence of Nitric Oxide-Sensing Systems in the Human Pathogen Vibrio vulnificus199203ENAbdelazizElgamlGraduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama UniversityShin-ichiMiyoshiGraduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Vibrio vulnificus is a halophilic estuarine bacterium, but this species causes fatal septicemia in humans. V. vulnificus may encounter many kinds of stresses either in the natural environment or in the human body. One of the striking stresses is the exposure to the reactive oxygen species including nitric oxide (NO). The present study revealed that NO could participate in the regulation of the V. vulnificus community behavior. When the bacterium was cultivated in the presence of sub-lethal doses of an NO donor, the expression of the genes encoding NO-detoxifying enzymes was significantly increased. The NO donor was also found to cause significant increase in production of a metalloprotease, a putative virulence factor, by the bacterium.No potential conflict of interest relevant to this article was reported.