Alterations of motility and chemotaxis in vitro and colonization in mice of fliG gene knockout mutant of Campylobacter jejuni

Campylobacter jejuni (C. jejuni) is a common causative pathogen of bacterial gastroenteritis in humans. Chemotaxis,a directional movement of bacteria towards suitable parasitic positions,is the initial key step for C. jejuni to achieve colonization on jejunal mucosa of hosts. The chemotactic migration was controlled and regulated by bacterial chemotaxis-associated two-component signaling system (che-TCS) in a MCPs→Ches→Flis/Mots manner. FliG,a member of Fli protein family,has been confirmed in some other bacterial pathogens to be a flagellar motor protein as well as an essential component of switch complex in bacterial flagellar motor. However,the function of FliG protein in chemotaxis of C. jejuni remains unknown. In the present study we generated a fliG gene knockout (fliG - ) mutant from C. jejuni strain NCTC11168 based on homologous recombination,and the motility,chemotaxis and colonization of fliG - mutant were subsequently determined. The motility test and chemotaxis test in vitro demonstrated that the diameters of colonies on semisolid agar plate and chemotactic rings towards 0. 2 mol/L sodium deoxycholate (SDC) on hard agar plus (HAP) of fliG-mutant were significantly smaller than those of the wild type strain (P 0. 05). Compared to the wild type strain,the numbers of fliG-mutant adhering to the surface of jejunal mucosa and existing in jejunal content of BALB/c-ByJ mice were also significantly decreased (P 0. 05). All the results of this study lead a conclusion that fliG is an essential gene for flagellar motility and chemotactic movement towards jejunal mucosa of C. jejuni during infection.