[S2] Host adaptation of pathogenic bacteria–doesn't bacteria want to cause disease?

[S2-5] Host adaptation and pathogenicity of Vibrio parahaemolyticus

○Toshio Kodama (Dept. Bacteriol., Inst. Trop. Med., Nagasaki Univ.)

Some Gram-negative bacterial pathogens equip sophisticated secretion systems to export proteins such as exotoxins and effectors. Numbers of exotoxins are exported to the exterior using a type II secretion system (T2SS). By contrast, type III secretion system (T3SS) can directly translocate effectors into the host cells. Those secretion systems and secreted proteins are considered as one of essential virulence determinants for the pathogens. However, to establish infection, these secretion systems are needed to be regulated by several regulatory mechanisms during a series of pathogenic processes. In this study, I focused on the host adaptation and the pathogenicity of Vibrio parahaemolyticus, which is known as a causative agent of food poisoning and a wound infection. This pathogen possesses some virulence factors including an exotoxin, thermostable direct hemolysin (TDH) and/or TDH-related hemolysin (TRH), and two sets of gene clusters for T3SSs (T3SS1 and T3SS2). Recent our functional analyses revealed that V. parahaemolyticus equips an outstanding mechanism for sensing the intestinal environment and the host cell contact in order to regulate precise expression and secretion of the T3SS effectors and the exotoxins. Further studies examining the molecular and regulatory mechanisms will help to understand the significance of existence and primary role of these virulence factors.