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Infection and Immunity, October 2002, p. 5355-5362, Vol. 70, No. 10
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.10.5355-5362.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

The Alternative Sigma Factor {sigma}E Plays an Important Role in Intestinal Survival and Virulence in Vibrio cholerae

Gabriela Kovacikova and Karen Skorupski*

Department of Microbiology and Immunology, Dartmouth Medical School, Hanover, New Hampshire 03755

Received 14 February 2002/ Returned for modification 14 May 2002/ Accepted 1 July 2002

The alternative sigma factor {sigma}E (RpoE) is involved in the response to extracytoplasmic stress and plays a role in the virulence of a variety of different bacteria. To assess the role of {sigma}E in Vibrio cholerae pathogenesis, a {Delta}rpoE mutant was constructed and analyzed using the infant mouse model. The results here show that {sigma}E contributes significantly to the virulence of V. cholerae. The {Delta}rpoE mutant was highly attenuated with a 50% lethal dose more than 3 logs higher than that for the parental strain, and its ability to colonize the intestine was reduced approximately 30-fold. A time course of infection revealed that the number of CFU of the {Delta}rpoE mutant was approximately 1 log lower than that of the parental strain by 12 h postinoculation and decreased further by 24 h. The defect in virulence in the {Delta}rpoE mutant thus appears to be a diminished ability to survive within the intestinal environment. The results here also show that {sigma}E is not required for growth and survival of V. cholerae in vitro at high temperatures but is required under other stressful conditions, such as in the presence of 3% ethanol. As in Escherichia coli, the expression of rpoE in V. cholerae is dependent upon two promoters located upstream of the gene, P1 and P2. P1 appears to be {sigma}70 dependent, whereas the downstream promoter, P2, is positively autoregulated by {sigma}E.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, Dartmouth Medical School, Hanover, NH 03755. Phone: (603) 650-1623. Fax: (603) 650-1318. E-mail: karen.skorupski{at}dartmouth.edu.

Editor: V. J. DiRita

Infection and Immunity, October 2002, p. 5355-5362, Vol. 70, No. 10
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.10.5355-5362.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



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