Advances on Vibrio parahaemolyticus research in the postgenomic era

Abstract

Vibrio parahaemolyticus is a leading cause of seafood‐borne bacterial gastroenteritis in humans. Since its discovery in 1950, this bacterium has been isolated in widespread outbreaks and in sporadic cases of gastroenteritis worldwide. Although the exotoxin, thermostable direct hemolysin, had been the focus of extensive research on the pathogenicity of V. parahaemolyticus, the whole‐genome sequencing of a clinical isolate, RIMD2210633 strain, was a breakthrough in this field. The possession of two sets of gene clusters for type III secretion systems (T3SS1 and T3SS2) was unveiled by that genome project. T3SS is a protein export apparatus that delivers bacterial proteins, called effectors, directly into the host's cytosol, to disrupt host cell function. The subsequent studies have established that T3SS2, which is encoded in an 80 kb pathogenicity island called V. parahaemolyticus pathogenicity island (Vp‐PAI), is closely related to enteropathogenicity. Recent functional analyses of Vp‐PAI‐encoded genes revealed the sophisticated mechanisms in V. parahaemolyticus for sensing the intestinal environment and host cell contact, and a dozen T3SS2‐exported proteins encoded in Vp‐PAI. In this review, we summarize recent advances in V. parahaemolyticus research regarding the control of the expression of Vp‐PAI‐encoded genes, structural components and the secretory regulation of T3SS2, and the biological activities of T3SS2‐exported effectors. Thus, Vp‐PAI‐encoded T3SS2 becomes an important key in the postgenomic era to shed light on the enteropathogenic mechanism of V. parahaemolyticus.

Identification of a family of Vibrio type III secretion system effectors that contain a conserved serine/threonine kinase domain

“…T3SS2 gene clusters are classified into three phylotypes (T3SS2α, T3SS2β and T3SS2γ) that are believed to have been acquired through horizontal gene transfer events (13,15,48). Even though VopG homologs are not universally found in all T3SS2 gene clusters, we identified VopG homologs in all three T3SS2 phylotypes.…”

“…Therefore, T3SS2 is considered a key V. parahaemolyticus virulence factor. Several T3SS2 related gene clusters have been identified in other Vibrio species and are referred to as T3SS2 phylotypes (T3SS2α, T3SS2β and T3SS2γ) (13). T3SS2α include T3SS2 gene clusters related to those found in the tdh-positive V. parahaemolyticus 5 pandemic strain RIMD2210633 and in V. cholerae strain AM-19226.…”

“…Ten T3SS2 effector proteins in V. parahaemolyticus have been identified to date (VopA, VopT, VopL, VopV, VopC, VopZ, VPA1380, VopO and the recently described "gatekeepers" VgpA and VgpB) (12,(16)(17)(18)(19)(20)(21)(22). These effectors subvert several cellular pathways including those controlling actin cytoskeleton dynamics and innate inflammatory responses (reviewed in (23)(24)(25)). These ten proteins are classified as either core or accessory T3SS2 effector proteins based on their distribution among the T3SS2 phylotypes (13).…”

“…These effectors subvert several cellular pathways including those controlling actin cytoskeleton dynamics and innate inflammatory responses (reviewed in (24)(25)(26)). These effector proteins are classified as either core or accessory T3SS2 effector proteins based on their distribution among the T3SS2 phylotypes (13).…”

“…The V. cholerae AM-19226 effector VopG had been classified as a V. cholerae specific T3SS effector (26, 45) but our analyses showed that VopG homologs belong to a larger family of putative effector proteins that is widely distributed among Vibrio species including V. parahaemolyticus, V. cholerae, V. mimicus and V. diabolicus as well as in strains of Shewanella baltica. Recently, Matsuda et al proposed to classify T3SS2 effectors proteins as "core" effectors if they are conserved in both V. parahaemolyticusand non-O1/non-O139 V. cholerae(13) and as "accessory" effectors (13) if they are not.…”