The mechanisms associated with the suppression of Vibrio parahaemolyticus cells in green-lipped mussels (Perna canaliculus).

The abundance of Vibrio parahaemolyticus in contaminated seafood correlates to an infectious dose, which is critical in the occurrence of vibriosis in humans. As V. parahaemolyticus does not infect healthy mussels, its interaction with microbiota of mussels can be a key determining factor in infectious dose and the causation of vibriosis in humans. Comparing 216 microbiomes of seawater, biofilms, and mussels over 1 year, we found that the composition of mussel microbiota is different compared to microbiotas of seawater and marine biofilms. Using an in situ approach, our results show that mussels with significantly low V. parahaemolyticus abundance possess a distinct microbiota in comparison with that of other mussels, biofilms, and seawater. This microbiota is 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 LIM domain-containing protein (Lin-11, Isl-1, and Mec-3) and immunoglobulin-like domain protein, constitutively induced only in mussels with low V. parahaemolyticus abundance regardless of mussel age or time of harvest. The LIM domain-containing protein showed significant interactions with a group of proteins involved in haemocyte differentiation and endosome biogenesis, key immunological processes. Our results suggest that the low abundance of V. parahaemolyticus in mussels likely results from interactions with the resident mussel microbiota and immunological responses of the host.