Two-Component System Response Regulator ompR Regulates Mussel Settlement through Exopolysaccharides

The outer membrane protein (OMP) is a kind of biofilm matrix component that widely exists in Gram-negative bacteria. However, the mechanism of OMP involved in the settlement of molluscs is still unclear. In this study, the mussel Mytilus coruscus was selected as a model to explore the function of ompR, a two-component system response regulator, on Pseudoalteromonas marina biofilm-forming capacity and the mussel settlement. The motility of the Delta ompR strain was increased, the biofilm-forming capacity was decreased, and the inducing activity of the Delta ompR biofilms in plantigrades decreased significantly (p < 0.05). The extracellular alpha-polysaccharide and beta-polysaccharide of the Delta ompR strain decreased by 57.27% and 62.63%, respectively. The inactivation of the ompR gene decreased the ompW gene expression and had no impact on envZ expression or c-di-GMP levels. Adding recombinant OmpW protein caused the recovery of biofilm-inducing activities, accompanied by the upregulation of exopolysaccharides. The findings deepen the understanding of the regulatory mechanism of bacterial two-component systems and the settlement of benthic animals.

Automated summary

In this study, the function of the two-component system response regulator ompR on biofilm formation and mussel settlement was investigated. The deletion of the ompR gene in Pseudoalteromonas marina resulted in increased motility, decreased biofilm-forming capacity, and reduced induction of plantigrade settlement in mussels. The levels of extracellular polysaccharides were also decreased in the delta ompR strain. Addition of recombinant OmpW protein restored biofilm-inducing activities and upregulated exopolysaccharides. These findings contribute to a better understanding of the regulatory mechanism of bacterial two-component systems and benthic animal settlement.