B-303. TAT Protein Export Pathway in Campylobacter jejuni
Gastroenteritis caused by Campylobacter species is the most common form of bacterial food poisoning in the US and world-wide accounting for up to $6 billion losses annually. Chickens are the primary source of human infections. Despite the progress in recent years, our understanding of the pathogenic process of C. jejuni lags behind compared to other enteric pathogens. In the present study we characterized the Twin-Arginine Translocation (TAT) pathway of C. jejuni. The TAT pathway exports folded proteins across the cytoplasmic membrane of bacteria via signal peptides with distinct motif (S/TRRxFLK). The TAT pathway contributes to bacterial stress responses leading to the survival of pathogenic bacteria in the environment or the host and is an important virulence mechanism in many medically important bacterial pathogens. Our examination of the C. jejuni genomes revealed tat gene homologs with one copy of tatA, tatB and tatC in all the strains. Fluorescence microscopy using TorA::GFP reporter indicated that GFP is exported to the periplasm in the wild type and the periplasmic localization was inhibited in the tatC mutant indicating the functional TAT system in C. jejuni. Further, the C. jejuni tatC mutant was impaired in motility and the electron microscopy of the tatC mutant revealed lack of flagellation. Importantly, the tatC mutant was defective in chicken colonization and no mutant bacteria were recovered by 7 days post inoculation in any of the tissues analyzed. These studies suggest that the TAT system is an important pathogenicity and/or colonization determinant of C. jejuni and that the TAT system and TAT-translocated proteins may represent novel targets for development of vaccines and non-conventional antimicrobials for human campylobacteriosis as well as to reduce chicken colonization, the natural source for human infection.