Mutation of rpoS gene decreased resistance to environmental stresses, synthesis of extracellular products and virulence of Vibrio anguillarum.
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 sigma factor, RpoS (sigma(S)), 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 degrees C in ASW), UV-irradiation and oxidative stress (5 mM H(2)O(2) 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 10(4) and 2.55 x 10(6) 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.
Ma
Li
L
Department of Marine Biology, College of Marine Life Science, Ocean University of China, Qingdao, China.
Chen
Jixiang
J
Liu
Rui
R
Zhang
Xiao-Hua
XH
Jiang
Ying-An
YA
D000222:Adaptation, Physiological / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000378:metabolism; D050296:Microbial Viability; D009154:Mutation; D009997:Osmotic Pressure; D018384:Oxidative Stress; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism; D013312:Stress, Physiological; D014733:Vibrio / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D014774:Virulence
D001426:Bacterial Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D012965:Sodium Chloride; D006861:Hydrogen Peroxide