LuxS/AI-2 Quorum Sensing System in Edwardsiella piscicida Promotes Biofilm Formation and Pathogenicity.

LuxS/AI-2 is an important quorum sensing system which affects the growth, biofilm formation, virulence, and metabolism of bacteria. LuxS is encoded by the gene, but how this gene is associated with a diverse array of physiological activities in () is not known. Here, we constructed an gene mutant strain, the △ strain, to identify how LuxS/AI-2 affects pathogenicity. The results showed that LuxS was not found in the gene mutant strain, and this gene deletion decreased growth compared to that of the wild-type strain. Meanwhile, the wild-type strain significantly increased penetration and motility in mucin compared to levels with the △ strain. The 50% lethal dose (LD) of the △ strain for zebrafish was significantly higher than that of the wild-type strain, which suggested that the gene deletion could attenuate the strain's virulence. The AI-2 activities of EIB202 were 56-fold higher than those in the △ strain, suggesting that the gene promotes AI-2 production. Transcriptome results demonstrated that between cells infected with the △ strain and those infected with the wild-type strain 46 genes were significantly differentially regulated, which included 34 upregulated genes and 12 downregulated genes. Among these genes, the largest number were closely related to cell immunity and signaling systems. In addition, the biofilm formation ability of EIB202 was significantly higher than that of the △ strain. The supernatant of EIB202 increased the biofilm formation ability of the △ strain, which suggested that the gene and its product LuxS enhanced biofilm formation in All results indicate that the LuxS/AI-2 quorum sensing system in promotes its pathogenicity through increasing a diverse array of physiological activities.