Vibrio parahaemolyticus cell biology and pathogenicity determinants

Abstract

Vibrio parahaemolyticus is a significant cause of gastroenteritis worldwide. Characterization of this pathogen has revealed a unique repertoire of virulence factors that allow for colonization of the human host and disease. The following describes the known pathogenicity determinants while establishing the need for continued research.

Fig. 1. Virulence Associated Factors of V. parahaemolyticus

A single flagellum at one pole of the bacterium is sheathed to extend the bacterial membrane and is required for swimming motility in liquid environments. During growth on semi-solid surfaces, flagella are produced along the lateral side of the bacterium, which aid in swarming motility. MAM7 is a multivalent adhesion protein that binds to fibronectin and phosphatidic acid, and it is required for the initial attachment to host cells. As shown simplistically, V. parahaemolyticus can utilize the siderophores vibrioferrin, ferrichrome, and aerobactin, along with heme, to scavenge iron from the environment. These iron transporters are internalized by different membrane receptors on the outer membrane of the bacteria and transported to the cytoplasm by different ABC complexes.

Fig. 2. Known toxins and type 3 secreted effectors of V. parahaemolyticus

The TDH and TLH toxins are secreted from the bacteria and form tetrameric pore complexes in the host membrane. These pores allow ions to flow freely across the host membrane which leads to hemolysis or cytotoxicity (left panel). V. parahaemolyticus translocates T3SS1 effectors (VopQ, VopR, VopS, and VPA0450) into host cells to cause cytotoxicity in different cell types such as macrophages and HeLa cells (middle panel). T3SS2 effectors (VopA, VopC, VopL, and VopT) are translocated into host cells to cause cytotoxicity of colon epithelial cells or enterotoxicity within the host (right panel).