Abundance of Vibrio parahaemolyticus in mussels is a result of synergistic effect between host microbiota and immune response of mussels. Abundance of Vibrio parahaemolyticus in mussels is a result of synergistic effect between host microbiota and immune response of mussels

The abundance of V. parahaemolyticus in contaminated seafood correlates to infectious dose, which is critical in outbreaks or sporadic infections. As V. parahaemolyticus can’t cause infections in healthy mussels or oysters, its interaction with the microbiota of mussels as well as interaction with its host plays an important role in the occurrence of vibriosis. In this study, we showed that the temperature of seawater is the major driver of microbial composition change in seawater, marine biofilm and mussel microbiota. Comparing 216 microbiomes of seawater, biofilms and mussels over one year, we found that the composition of mussels microbiota is not significantly influenced by microbiomes of seawater and biofilms. Using in situ approach, our results show that mussels with significantly low V. parahaemolyticus abundance have distinct microbiota, characterized by species of known vibriocidal status (e.g. Pseudomonas spp.) and species of unknown vibriocidal status (e.g. Campylobacterota, Bacteroides massiliensis, Lancefieldella, Erysipelotrichales, Faecalibacterium, and Catenibacterium). Examining proteomes of mussels, we discovered two proteins, the LMN domain-containing protein and immunoglobulin-like domain protein, constitutively induced only in mussels with low V. parahaemolyticus abundance regardless of mussels age or time of harvest. The LMN domain-containing protein showed significant interactions with a group of proteins involved in hemocyte differentiation and endosome biogenesis, key immunological processes. Our results suggest that the low abundance of V. parahaemolyticus in mussels is a result of the synergistic effect between host microbiota and the immune response of mussels.