AphA is a small PadR-family DNA-binding regulator in vibrios. AphA has been shown to be involved in transcriptional auto-repression, intestinal colonization and lethality in mice, biofilm formation, and quorum sensing in Vibrio cholerae. The AphA protein of Vibrio parahaemolyticus has 85% identity to that of V. cholerae with the same number of amino acids. In this work, the aphA null mutant was constructed from a wild-type pandemic strain of V. parahaemolyticus for characterization of the phenotypic changes. AphA is required for biofilm formation in V. parahaemolyticus, and a decreased production of biofilm exopolysaccharide matrix in the aphA mutant relative to the wild-type parent strain accounts for its reduced biofilm formation. AphA is also necessary for the optimal swimming and swarming motility of V. parahaemolyticus. In addition, AphA is essential for lethality in mice and cytotoxic activity, but the aphA deletion did not have effect on enterotoxicity.
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