title: Alternative sigma factor RpoE is important for Vibrio parahaemolyticus cell envelope stress response and intestinal colonization.
abstract: Vibrio parahaemolyticus is a halophile that inhabits brackish waters and a wide range of hosts, including crustaceans, fish, mollusks, and humans. In humans, it is the leading cause of bacterial seafood-borne gastroenteritis. The focus of this work was to determine the role of alternative sigma factors in the stress response of V. parahaemolyticus RIMD2210633, an O3:K6 pandemic isolate. Bioinformatics identified five putative extracytoplasmic function (ECF) family of alternative sigma factors: VP0055, VP2210, VP2358, VP2578, and VPA1690. ECF factors typically respond to cell wall/cell envelope stress, iron levels, and the oxidation state of the cell. We have demonstrated here that one such sigma factor, VP2578, a homologue of RpoE from Escherichia coli, is important for survival under a number of cell envelope stress conditions and in gastrointestinal colonization of a streptomycin-treated adult mouse. In this study, we determined that an rpoE deletion mutant strain BHM2578 compared to the wild type (WT) was significantly more sensitive to polymyxin B, ethanol, and high-temperature stresses. We demonstrated that in in vivo competition assays between the rpoE mutant and the WT marked with the β-galactosidase gene lacZ (WBWlacZ), the mutant strain was defective in colonization compared to the WT. In contrast, deletion of the rpoS stress response regulator did not affect in vivo survival. In addition, we examined the role of the outer membrane protein, OmpU, which in V. cholerae is proposed to be the sole activator of RpoE. We found that an ompU deletion mutant was sensitive to bile salt stress but resistant to polymyxin B stress, indicating OmpU is not essential for the cell envelope stress responses or RpoE function. Overall, these data demonstrate that RpoE is a key cell envelope stress response regulator and, similar to E. coli, RpoE may have several factors that stimulate its function.
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, Delaware, USA.
authors.forename: Brandy
authors.initials: B
authors.lastname: Haines-Menges
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, Delaware, USA.
authors.forename: W Brian
authors.initials: WB
authors.lastname: Whitaker
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, Delaware, USA fboyd@udel.edu.
authors.forename: E Fidelma
authors.initials: EF
authors.lastname: Boyd
mesh_terms: D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D002473:Cell Wall / Q000378:metabolism / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000382:microbiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010802:Phylogeny; D011112:Polymyxin B / Q000378:metabolism; D017384:Sequence Deletion / Q000235:genetics; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological / Q000235:genetics / Q000502:physiology*; D014736:Vibrio parahaemolyticus / Q000235:genetics / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D012808:Sigma Factor; D000431:Ethanol; D001616:beta-Galactosidase; D011112:Polymyxin B