Mussel settlement mediated by calcined mussel shell powder through outer membrane protein gene ompW

Calcined mussel shell powder (CMSP) is an environmentally friendly coating material to inhibit mussel settlement, making it a potential sustainable strategy against marine biofouling. However, the molecular mechanism by which CMSP mediates mussel settlement is still unclear. This study aimed to investigate how CMSP coating affects the settlement of Mytilus coruscus through the outer membrane protein gene ompW. In this study, the marine bacterium Pseudoalteromonas marina, which exhibited stable induction activity on mussel settlement, was used as the test strain. Our results showed that CMSP coating regulated the levels of Ca²⁺ in seawater to influence the expression of the outer membrane protein OmpW. Notably, after the ompW gene was deleted, the production of extracellular polymeric substances (EPS) was significantly reduced, and the induction activity of the ΔompW biofilm decreased by 38.33%. Upon the analysis of EPS, it was discovered that the colanic acid content in the biofilm of ΔompW strain was significantly decreased by 70.92% compared to that in P.marina biofilm. Interestingly, the OmpW protein alone did not induce the settlement of plantigrades directly, the levels of extracellular polysaccharides and induction activity were restored to those of the wild-type biofilm when 10 mg/L OmpW were added to the ΔompW biofilm. This suggests that CMSP regulates extracellular polysaccharides through the outer membrane protein gene ompW, which in turn mediates mussel settlement. These findings provide further insight into the mechanism by which CMSP inhibits the settlement of fouling organisms and the interaction between OmpW and marine invertebrates.