Data from: The contribution of marine aggregate-associated bacteria to the accumulation of pathogenic bacteria in oysters: an agent-based model

Bivalves process large volumes of water, leading to their accumulation of bacteria, including potential human pathogens (e.g., vibrios). These bacteria are captured at low efficiencies when freely suspended in the water column, but they also attach to marine aggregates, which are captured with near 100% efficiency. For this reason, and because they are often enriched with heterotrophic bacteria, marine aggregates have been hypothesized to function as important transporters of bacteria into bivalves. The relative contribution of aggregates and unattached bacteria to the accumulation of these cells, however, is unknown. We developed an agent-based model to simulate accumulation of vibrio-type bacteria in oysters. Simulations were conducted over a realistic range of concentrations of bacteria and aggregates and incorporated the dependence of pseudofeces production on particulate matter. The model shows that the contribution of aggregate-attached bacteria depends strongly on the unattached bacteria, which form the colonization pool for aggregates and are directly captured by the simulated oysters. The concentration of aggregates is also important, but its effect depends on the concentration of unattached bacteria. At high bacterial concentrations, aggregates contribute the majority of bacteria in the oysters. At low concentrations of unattached bacteria, aggregates have a neutral or even a slightly negative effect on bacterial accumulation. These results provide the first evidence suggesting that the concentration of aggregates could influence uptake of pathogenic bacteria in bivalves and show that the tendency of a bacterial species to remain attached to aggregates is a key factor for understanding species-specific accumulation.双壳贝类(Bivalves)会过滤大量水体，因此会在体内积累细菌，包括潜在的人类致病菌（例如弧菌(vibrios)）。这类细菌若自由悬浮于水柱中，被捕食的效率较低，但它们也会附着在海洋聚集体(marine aggregates)上，而后者的被捕食效率接近100%。基于此，再加上海洋聚集体通常会富集异养细菌，已有假说提出海洋聚集体是细菌向双壳贝类体内转运的重要载体。不过，海洋聚集体与游离细菌对双壳贝类体内这类细菌积累的相对贡献仍不明晰。我们开发了一款基于智能体的模型(agent-based model)，用于模拟牡蛎体内弧菌类细菌的积累过程。模拟实验在符合现实场景的细菌与聚集体浓度范围内开展，并且纳入了伪粪(pseudofeces)产生量与颗粒物的依赖关系。该模型显示，附着于聚集体的细菌的贡献很大程度上取决于游离细菌：后者既是聚集体的定殖池，同时也会被模拟的牡蛎直接捕获。聚集体的浓度同样会产生影响，但其作用效果依赖于游离细菌的浓度。当细菌浓度较高时，聚集体贡献了牡蛎体内的大部分细菌；而当游离细菌浓度较低时，聚集体对细菌积累甚至会产生中性乃至略微的负向影响。本研究首次提供证据表明，海洋聚集体的浓度可能会影响双壳贝类对致病菌的摄取，同时揭示了细菌物种保持附着于聚集体的倾向，是理解物种特异性细菌积累的关键因素。