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Journal of Bacteriology, September 2006, p. 6490-6497, Vol. 188, No. 18
0021-9193/06/$08.00+0     doi:10.1128/JB.00533-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

AphB Influences Acid Tolerance of Vibrio vulnificus by Activating Expression of the Positive Regulator CadC

Jee Eun Rhee, Hee Gon Jeong, Jeong Hyun Lee, and Sang Ho Choi*

Department of Food Science and Technology, School of Agricultural Biotechnology, Center for Agricultural Biomaterials, Seoul National University, Seoul 151-742, South Korea

Received 14 April 2006/ Accepted 3 July 2006

A mutant of Vibrio vulnificus that was more sensitive to low pH was screened from a library of mutants constructed by random transposon mutagenesis. By use of a transposon-tagging method, an open reading frame encoding a LysR homologue, AphB, was identified and cloned from V. vulnificus. The deduced amino acid sequence of AphB from V. vulnificus was 80% identical to that reported from V. cholerae. A mutational analysis demonstrated that the gene product of aphB contributes to acid tolerance of V. vulnificus. The lysine decarboxylase activity and cellular level of the cadA transcript were decreased in the aphB mutant, indicating that AphB exerts its effect on the acid tolerance of V. vulnificus by enhancing the expression of cadBA. Western blot analyses demonstrated that the cellular level of CadC, a transcription activator of the cadBA operon, was significantly reduced by aphB mutation, and a primer extension analysis revealed that the cadC promoter (PcadC) activity was under the positive control of AphB. A direct interaction between AphB and the PcadC DNA was demonstrated by gel mobility shift assays. The AphB binding site mapped by deletion analyses of the PcadC regulatory region and confirmed by a DNase I protection assay was centered at the 61.5 bp upstream of the transcription start site. Accordingly, these results demonstrate that AphB and CadC function sequentially in a regulatory cascade to activate cadBA expression and that AphB activates the expression of cadC by directly binding to an upstream region of PcadC.

* Corresponding author. Mailing address: Department of Food Science and Technology, School of Agricultural Biotechnology, Center for Agricultural Biomaterials, Seoul National University, Seoul, 151-742, South Korea. Phone: 82-2-880-4857. Fax: 82-2-873-5095. E-mail: choish{at}snu.ac.kr.

Journal of Bacteriology, September 2006, p. 6490-6497, Vol. 188, No. 18
0021-9193/06/$08.00+0     doi:10.1128/JB.00533-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Jones, M. K., Oliver, J. D. (2009). Vibrio vulnificus: Disease and Pathogenesis. Infect. Immun. 77: 1723-1733 [Full Text]  
  • Oh, M. H., Lee, S. M., Lee, D. H., Choi, S. H. (2009). Regulation of the Vibrio vulnificus hupA Gene by Temperature Alteration and Cyclic AMP Receptor Protein and Evaluation of Its Role in Virulence. Infect. Immun. 77: 1208-1215 [Abstract] [Full Text]  
  • Jeong, H. G., Choi, S. H. (2008). Evidence that AphB, Essential for the Virulence of Vibrio vulnificus, Is a Global Regulator. J. Bacteriol. 190: 3768-3773 [Abstract] [Full Text]  
  • Jones, M. K., Warner, E., Oliver, J. D. (2008). Survival of and In Situ Gene Expression by Vibrio vulnificus at Varying Salinities in Estuarine Environments. Appl. Environ. Microbiol. 74: 182-187 [Abstract] [Full Text]  


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