Microbial Community and Vibrio parahaemolyticus Population Dynamics in Relayed Oysters. Co-variation between oyster microbiota and Vibrio parahaemolyticus

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.

以滤食为生的双壳类软体动物（如牡蛎）通常会定植人类致病海洋细菌副溶血性弧菌（Vibrio parahaemolyticus, Vp）。本研究针对一种名为转养（relay）的采后处理策略所涉及的牡蛎与水体样本展开分析：该策略是将副溶血性弧菌浓度较高的牡蛎转移至盐度升高且副溶血性弧菌浓度较低的水体中，以深入解析牡蛎体内副溶血性弧菌与菌群的互作关系。本研究同时探究了河口天然菌群的组成，及其对转养牡蛎微生物群落结构变化的影响。本研究通过16S rRNA基因测序技术，分析了转养14天后牡蛎样本的物种类群丰度变化。结合竞争实验开展丰度与相关性分析，以筛选出转养过程中与副溶血性弧菌丰度降低呈共变关系的牡蛎微生物组类群。在副溶血性弧菌丰度自第0天至第14天降幅最显著的牡蛎样本中，共有27个菌属在转养过程中丰度上升。弧菌属（Vibrio）是操作分类单元（Operational Taxonomic Unit, OTU）丰度最高的菌属，且16S rRNA基因序列丰度与牡蛎体内副溶血性弧菌浓度呈负相关。体外竞争实验显示，10株受试菌株中有两株——溶藻弧菌（Vibrio alginolyticus）与果胶弧菌（Vibrio pectinicida）——的平均细胞计数高于副溶血性弧菌。本研究结果表明，相较于非弧菌属类群，其他弧菌属物种更能够在转养过程中清除牡蛎体内定植的副溶血性弧菌。后续需在牡蛎基质中开展针对体外可竞争抑制副溶血性弧菌的弧菌属物种的相关研究。