Roles of LuxR in regulating extracellular alkaline serine protease A, extracellular polysaccharide and mobility of Vibrio alginolyticus

Abstract

In marine Vibrio species, the Vibrio harveyi-type LuxR protein, a key player in a quorum-sensing system, controls the expression of various genes. In this study, the luxR homologue in Vibrio alginolyticus was identified and named luxRval, whose expression was greatly induced by the increase of cell number. The luxRval in-frame deletion mutant showed a significant downregulation of total extracellular protease activity, and especially caused a 70% decrease in the transcript levels of extracellular alkaline serine protease A (proA), which was an important virulent factor of V. alginolyticus. Complementation in trans with luxRval could restore the expression of proA to the level of the wild-type strain. Deletion of the luxRval gene also resulted in changes of colony morphology, extracellular polysaccharide production and mobility. Therefore, another member of the V. harveyi-type LuxR regulator family has been characterized in V. alginolyticus. © 2008 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.