Microbial Community and Vibrio parahaemolyticus Population Dynamics in Relayed Oysters

Filter-feeding bivalve shellfish such as oysters are routinely inhabited by the human pathogenic marine bacterium Vibrio parahaemolyticus (Vp). We analyzed oyster and water samples utilized in a post-harvest strategy known as relay, where oysters with higher concentrations of Vp are translocated to water of elevated salinity and with low Vp concentrations, to better understand the Vibrio parahaemolyticus - flora interaction in the oyster. Within we investigate the natural microbiota of the estuarine water and there effect on microbial community member shifts in relayed oysters. Oyster samples were analyzed for shifts in taxa after 14 days of relay using 16S rRNA gene sequences. Abundance and correlation analyses were performed in conjunction with a competition assay to investigate taxa within the oyster microbiome that co-vary with the reduction of Vp during relay. Twenty-seven genera increased in abundance during relay in the oyster samples that showed the largest decrease in Vp from day 0 to day 14. The Vibrio genus had the highest abundance per OTU and 16S rRNA gene sequence abundance was inversely correlated to oyster Vp concentrations. In vitro competition assays resulted in two of ten species (Vibrio alginolyticus and Vibrio pectinicida) with higher average cell counts compared to V. parahemolyticus. Evidenced by the assays in this study other Vibrio species in comparison to non-Vibrio genera are best equipped to extinguish colonized Vp from the oyster during relay. Further research with Vibrio spp. that outcompete Vp in vitro needs to be carried out in oyster matrices.