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Journal of Bacteriology, January 2006, p. 794-800, Vol. 188, No. 2
0021-9193/06/$08.00+0     doi:10.1128/JB.188.2.794-800.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

A Vibrio cholerae Relaxed (relA) Mutant Expresses Major Virulence Factors, Exhibits Biofilm Formation and Motility, and Colonizes the Suckling Mouse Intestine

Anisia J. Silva and Jorge A. Benitez*

Morehouse School of Medicine, Department of Microbiology, Biochemistry and Immunology, 720 Westview Dr., SW, Atlanta, Georgia 30310-1495

Received 20 July 2005/ Accepted 18 October 2005

We have constructed a relaxed mutant of El Tor biotype Vibrio cholerae strain C7258 by disruption of the RelA catalytic domain. The ability of the V. cholerae relaxed mutant to biosynthesize guanosine tetraphosphate and pentaphosphate was severely affected; the mutant showed a reduced growth rate in minimal medium that could be reversed by the addition of Casamino Acids, and it was thermosensitive. Contrary to published findings, the new relA mutant still produced significant cholera toxin and toxin-coregulated pilus. The V. cholerae relA mutant was motile, produced normal biofilms, and colonized the suckling mouse intestine. Our data suggest that levels of basal guanosine nucleotides pppGpp and ppGpp, rather than the availability of a stringent response, could influence expression of virulence factors, depending on strain and culture conditions. Production of hemagglutinin (HA)/protease, which requires HapR, RpoS, and the cyclic AMP receptor protein, was not strongly affected. Nevertheless, overexpression of RelA protein from an isopropyl-ß-D-thiogalactopyranoside-inducible promoter posttranscriptionally diminished production of HA/protease.

* Corresponding author. Mailing address: Morehouse School of Medicine, Department of Microbiology, Biochemistry and Immunology, 720 Westview Dr., SW, Atlanta, GA 30310-1495. Phone: (404) 756-6661. Fax: (404) 752-1179. E-mail: jbenitez{at}msm.edu.

Journal of Bacteriology, January 2006, p. 794-800, Vol. 188, No. 2
0021-9193/06/$08.00+0     doi:10.1128/JB.188.2.794-800.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Silva, A. J., Sultan, S. Z., Liang, W., Benitez, J. A. (2008). Role of the Histone-Like Nucleoid Structuring Protein in the Regulation of rpoS and RpoS-Dependent Genes in Vibrio cholerae. J. Bacteriol. 190: 7335-7345 [Abstract] [Full Text]  
  • Nascimento, M. M., Lemos, J. A., Abranches, J., Lin, V. K., Burne, R. A. (2008). Role of RelA of Streptococcus mutans in Global Control of Gene Expression. J. Bacteriol. 190: 28-36 [Abstract] [Full Text]  
  • Jahid, I. K., Silva, A. J., Benitez, J. A. (2006). Polyphosphate Stores Enhance the Ability of Vibrio cholerae To Overcome Environmental Stresses in a Low-Phosphate Environment. Appl. Environ. Microbiol. 72: 7043-7049 [Abstract] [Full Text]  
  • Thompson, F. L., Klose, K. E., the AVIB Group, (2006). Vibrio2005: the First International Conference on the Biology of Vibrios. J. Bacteriol. 188: 4592-4596 [Full Text]  


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