Copper stress by nutritional immunity activates the CusS-CusR two-component system that contributes to Vibrio alginolyticus anti-host response but affects virulence-related properties

Abstract

Abstract Copper is indispensable for cellular functions, but high levels of copper will destruct biological macromolecules. Copper accumulation was recently found to appear where the bacterial infection took place. This proved that copper resistance is necessary for bacteria virulence. Almost all bacteria, from isolated environmental bacteria to human pathogenic bacteria, have copper tolerance mechanisms. We found Vibrio alginolyticus, an emerging microbe distributed widely in tropical coastal areas, had the copper resistance phosphate regulon CusS-CusR-CusCFBA. After Cu2+ treatment, the expression of cusS, cusR, cusCFBA, copB and [EC:3.6.3.4] were significantly up-regulated. These genes were related to copper tolerance, among which cusS and cusR played a key role. When cusS and cusR were silenced, the expression levels of cusCFBA were also significantly decreased. Unexpectedly, the adhesion, hemolysis, biofilm formation, motility, and virulence were significantly increased in the silencing strains of cusS and cusR. Meanwhile, promoter region analysis, EMSA, and LacZ reporter gene analysis suggested that CusR played a role in the regulation of cusCFBA and multiple virulence genes. Together, these indicated that although CusSR could confer resistance to the host defense by regulating the cusCFBA to participate in the copper tolerance mechanism, the activation of the CusSR by copper stress from nutritional immunity would reduce the V. alginolyticus pathogenesis.