원문정보
초록
영어
Vibrio vulnificus, a human pathogen, exhibits a biofilm-forming activity and its ability requires global regulators, NtrC and RpoN. Both transcription factors regulate lipopolysaccharide (LPS) production and swimming motility, which are critically required for the initial stages of biofilm formation. In addition, exopolysaccharide (EPS) production is also influenced by these regulators. Thus, in this study, the relationships among the regulators, the genes encoding EPS biosyntheses, and their pathogenic roles were investigated to elucidate the complex but elaborate processes of biofilm formation by this pathogen. EPS production was highly induced under the nitrogen starvation conditions, and its induction required the presence of functional NtrC and RpoN. The gene clusters necessary for syntheses of EPS and capsular polysaccharide (CPS) were screened through in silico analysis of V. vulnificus genome sequences. Three clusters for EPS and a cluster for CPS were isolated, and their transcriptional characteristics were investigated. Only the EPS clusters were controlled by NtrC and RpoN, and their expression was significantly increased under the nitrogen starvation condition. The mutants deficient in one of the genes within each cluster showed decreased production of EPS and attenuated ability to form mature biofilm. Furthermore, these mutants showed significantly less adherence to the human epithelial cells than their isogenic wildtype, and one of the mutant exhibited decreased cytotoxicity to human cell lines. These results suggest that NtrC/RpoN-regulated EPS is the critical factors for biofilm formation and adherence of V. vulnificus