Outer membrane vesicles induce the mussel plantigrade settlement via regulation of c-di-GMP.

Despite the importance of outer membrane vesicles (OMVs) in benthic animal settlement, the underlying molecular mechanism remains elusive. Here, the impact of OMVs and OMVs synthesis-related gene in plantigrade settlement was tested. The OMVs were extracted from through density gradient centrifugation, and a knockout strain, achieved by homologous recombination, was utilized for the investigation. Our results demonstrated that OMVs could significantly enhance plantigrades settlement. Deleting the resulted in downregulation of c-di-GMP, accompanied by a reduction of OMV production, a decline in bacterial motility and increasing biofilm-forming ability. Enzyme treatment resulted in a 61.11% reduction in OMV-inducing activity and a 94.87% reduction in LPS content. Thus, OMVs regulate mussel settlement LPS, and c-di-GMP is responsible for the OMV-inducing capacity. These findings provide new insights into the interactions between bacteria and mussels.