Evidence that the Vibrio vulnificus flagellar regulator FlhF is regulated by a quorum sensing master regulator SmcR.
A single polar flagellum and motility are potential virulence factors of Vibrio vulnificus, a foodborne pathogen. In the present study, the functions of FlhF and regulatory characteristics of the flhF expression of V. vulnificus were investigated. A deletion mutation in flhF abolished motility, flagella formation and flagellin synthesis, and introduction of flhF in trans complemented the defects. The flhF mutant revealed decreased expression of the class III and IV flagella genes, indicating that FlhF is a key regulator for the flagellar biogenesis of V. vulnificus. The influence of global regulatory proteins on the expression of flhF was examined and SmcR, a LuxR homologue, was found to downregulate flhF expression at the transcriptional level. SmcR represses flhF expression only in the stationary phase of growth and exerts its effects by directly binding to the flhF promoter region. Finally, an SmcR binding site, centred at 22.5 bp upstream of the transcription start site, was identified by a DNase I protection assay. The combined results demonstrate that a quorum sensing master regulator SmcR influences the motility and flagellar biogenesis of V. vulnificus through modulating the expression of FlhF in a growth-phase-dependent manner.
National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul 151-921, Republic of Korea.
Seung Min
SM
Kim
National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul 151-921, Republic of Korea.
Dong Hwan
DH
Lee
National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul 151-921, Republic of Korea.
Sang Ho
SH
Choi
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D005407:Flagella / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D053038:Quorum Sensing; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D041261:Vibrio vulnificus / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
D001426:Bacterial Proteins; D015534:Trans-Activators; C410093:smcR protein, Vibrio vulnificus; C078317:flhF protein, Bacteria; D020559:Monomeric GTP-Binding Proteins