Open AccessControl of the Type 3 Secretion System in Vibrio harveyi by Quorum Sensing through Repression of ExsA
Author(s) -
Christopher M. Waters,
Julie Tsu-Yu Wu,
Meghan E. Ramsey,
Rebecca Harris,
Bonnie L. Bassler
Publication year - 2010
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.00886-10
Subject(s) - vibrio harveyi , regulon , psychological repression , quorum sensing , biology , operon , type three secretion system , gene , autoinducer , regulation of gene expression , repressor , complementation , microbiology and biotechnology , genetics , gene expression , mutant , vibrio , virulence , bacteria
The type 3 secretion system (T3SS) genes ofVibrio harveyi are activated at low cell density and repressed at high cell density by quorum sensing (QS). Repression requires LuxR, the master transcriptional regulator of QS-controlled genes. Here, we determine the mechanism underlying the LuxR repression of the T3SS system. Using a fluorescence-based cell sorting approach, we isolatedV. harveyi mutants that are unable to express T3SS genes at low cell density and identified two mutations in theV. harveyi exsBA operon. While LuxR directly represses the expression ofexsBA , complementation and epistasis analyses reveal that it is the repression ofexsA expression, but notexsB expression, that is responsible for the QS-mediated repression of T3SS genes at high cell density. The present work further defines the genes in theV. harveyi QS regulon and elucidates a mechanism demonstrating how multiple regulators can be linked in series to direct the expression of QS target genes specifically at low or high cell density.