The role of proteins expressed under the stress condition in virulence of some Vibrio strains.

In order to survive in changing environments, bacteria possess enormous adaptive capabilities that allow them to modulate their behavior and reprogram gene expression in response to environmental cues. Vibrios are inhabitants of estuarine and fresh waters and some species are pathogenic to humans, and marine vertebrates and invertebrates. Surface attachment is believed to be essential for colonization of all of these natural environments. Vibrio (V.) parahaemolyticus, an ubiquitous marine bacterium and human pathogen, seems to be particularly adapted to growth on surfaces or in biofilms. In response to its physical environment, V. parahaemolyticus induces the expression of a large number of genes. The purpose of the present study was to investigate the influence of different physicochemical parameters (temperature and osmolarity) on the virulence factors expression in Vibrio strains using different conditions simulating environmental stress factors. Some of the tested strains displayed a decreased adherence capacity to the inert substrate under stressful conditions, and the adherence capacity on HeLa cell was generally reduced, while the soluble enzymatic factors showed only slight changes. However, it is to be noticed that the haemolysins and Kanagawa enterotoxin were better expressed at higher temperature and osmolarity, these factors probably contributing to the bacterial adaptation and survival in the extern medium of certain Vibrio species.