Mutation of rpoS gene decreased resistance to environmental stresses, synthesis of extracellular products and virulence of Vibrio anguillarum

• Published in: FEMS microbiology ecology Vol. 70; no. 2; pp. 286 - 292
• Main Authors: Ma, Li, Chen, Jixiang, Liu, Rui, Zhang, Xiao-Hua, Jiang, Ying-An
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.11.2009; Blackwell Publishing Ltd; Oxford University Press
• Subjects: Adaptation, Physiological - genetics; Aquatic animals; Artificial seawater; Bacteria; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Catalase; Cloning, Molecular; Danio rerio; Ecology; Environmental stress; environmental stresses; Fish; Freshwater; Freshwater fish; Gene Expression Regulation, Bacterial; Genes, Bacterial; Gram-negative bacteria; Harsh environments; High temperature; Homologous recombination; Homology; Hot Temperature; Hydrogen peroxide; Hydrogen Peroxide - metabolism; Irradiation; Lethal dose; Lipase; Marine; Marine fish; Microbial Viability; Microbiology; Mutants; Mutation; Osmotic Pressure; Osmotic stress; Oxidative Stress; Pathogenicity; Pathogens; Phospholipase; rpoS mutant; Seawater; Sensitivity; Sigma Factor - genetics; Sigma Factor - metabolism; Sodium chloride; Sodium Chloride - metabolism; Stress, Physiological; Ultraviolet radiation; Vibrio - enzymology; Vibrio - genetics; Vibrio - pathogenicity; Vibrio - physiology; Vibrio anguillarum; Vibriosis; Virulence; Waterborne diseases; virulence; mutant; environmental stresses
• ISSN: 0168-6496; 1574-6941
• DOI: 10.1111/j.1574-6941.2009.00713.x

Vibrio anguillarum is a gram-negative halophilic bacterium that causes vibriosis in marine fish, freshwater fish and other aquatic animals. Bacteria have developed strategies to survive in harsh environments. The alternative σ factor, RpoS (σS), plays a key role in surviving under stress conditions in some gram-negative bacteria. An rpoS mutant of pathogenic V. anguillarum W-1 was constructed by homologous recombination. The sensitivity of the rpoS mutant to osmotic stress [2.4 M NaCl in artificial seawater (ASW)] did not change obviously, but the sensitivity of the rpoS mutant to high temperature (45 °C in ASW), UV-irradiation and oxidative stress (5 mM H₂O₂ in ASW) increased 33-fold, sixfold and 10-fold, respectively. The production of extracellular phospholipase, diastase, lipase, caseinase, hemolysin, catalase and protease of the rpoS mutant decreased markedly compared with those of the wild-type strain. Virulence of the rpoS mutant strain was also decreased when it was inoculated intraperitoneally into zebra fish; the lethal dose 50% of the wild type and the mutant was 8.66 x 10⁴ and 2.55 x 10⁶ CFU per fish, respectively. These results indicated that the RpoS of V. anguillarum plays important roles in bacterial adaptation to environmental stresses and its pathogenicity.