RpoS-Dependent Stress Response and Exoenzyme Production in Vibrio vulnificus

Abstract

Vibrio vulnificus is an estuarine bacterium capable of causing rapidly fatal infections through both ingestion and wound infection. Like other opportunistic pathogens, V. vulnificus must adapt to potentially stressful environmental changes while living freely in seawater, upon colonization of the oyster gut, and upon infection of such diverse hosts as humans and eels. In order to begin to understand the ability of V. vulnificus to respond to such stresses, we examined the role of the alternate sigma factor RpoS, which is important in stress response and virulence in many pathogens. An rpoS mutant of V. vulnificus strain C7184o was constructed by homologous recombination. The mutant strain exhibited a decreased ability to survive diverse environmental stresses, including exposure to hydrogen peroxide, hyperosmolarity, and acidic conditions. The most striking difference was a high sensitivity of the mutant to hydrogen peroxide. Albuminase, caseinase, and elastase activity were detected in the wild type but not in the mutant strain, and an additional two hydrolytic activities (collagenase and gelatinase) were reduced in the mutant strain compared to the wild type. Additionally, the motility of the rpoS mutant was severely diminished. Overall, these studies suggest that rpoS in V. vulnificus is important for adaptation to environmental changes and may have a role in virulence.

Deep-sea hydrothermal vent bacteria related to human pathogenic Vibrio species

“…S4). CDSs shared with V. parahaemolyticus (3,973) and V. vulnificus (3,309) corresponded to 82% and 84.5% of the V. parahaemolyticus and V. alginolyticus genomes. Analyses of shared gene content indicated V. antiquarius, V. alginolyticus, and V. parahaemolyticus are about equidistant (Fig.…”

“…Vibrio cholerae is the most notorious because it is the causative agent of cholera. Vibrio vulnificus and Vibrio parahaemolyticus cause severe illness in humans and are associated with consumption of contaminated seafood (3,4). Vibrio harveyi (5), Vibrio anguillarum (6, 7), and V. parahaemolyticus (8) continue to cause substantial economic losses to the aquaculture industry worldwide.…”

Vibrio vulnificus Vulnibactin, But Not Metalloprotease VvpE, Is Essentially Required for Iron-Uptake from Human Holotransferrin

“…Without exception, reports issued to date demonstrate that VvpE expression occurs during the late exponential or stationary growth phase. [34][35][36][37] These results evidently indicate that VvpE is not involved in facilitating vulnibactin-mediated iron-assimilation via the proteolytic cleavage of transferrins. DF-HI broth containing HT as an iron source and human body fluids present an iron-limited condition because transferrin-bound iron is not freely available for V. vulnificus.…”

Survival of and In Situ Gene Expression by Vibrio vulnificus at Varying Salinities in Estuarine Environments

“…Thus, in situ studies using cells constrained in membrane diffusion chambers, particularly involving the VBNC state, have also been conducted in order to examine the survival of V. vulnificus in the environment (27). While such studies are valuable in characterizing the survival of bacteria in natural environments, they generally rely on simple plate counts and offer no insight into the gene expression occurring during growth and/or survival.Of the few studies that have investigated gene expression in V. vulnificus, most have been conducted under select physiological conditions in an attempt to identify altered niche-related phenotypes on the basis of select gene inactivation (12,31,32,34,35). However, many traits contribute to ecological survival and such studies are likely to overlook subtle changes that would occur in the bacterium's natural environment.…”

“…Of the few studies that have investigated gene expression in V. vulnificus, most have been conducted under select physiological conditions in an attempt to identify altered niche-related phenotypes on the basis of select gene inactivation (12,31,32,34,35). However, many traits contribute to ecological survival and such studies are likely to overlook subtle changes that would occur in the bacterium's natural environment.…”