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.

双壳类软体动物（Bivalves）会过滤大量水体，进而在体内积累细菌，其中包含潜在的人类致病细菌（pathogenic bacteria），例如弧菌（vibrios）。这些细菌在自由悬浮于水体中时，被捕获的效率较低；但它们也会附着在海洋聚集体（marine aggregates）上，而这类聚集体的捕获效率接近100%。出于这一原因，再加上海洋聚集体通常会富集异养细菌（heterotrophic bacteria），学界曾提出假说，认为海洋聚集体是细菌向双壳类软体动物体内转运的重要载体。然而，海洋聚集体与游离细菌对这类细菌积累的相对贡献仍不明确。我们开发了一种基于智能体的模型（agent-based model），以模拟牡蛎（oysters）体内弧菌类细菌的积累过程。模拟实验在符合实际的细菌与聚集体浓度范围内开展，并纳入了假粪（pseudofeces）生成量对颗粒物的依赖关系。模型结果显示，附着于聚集体的细菌的贡献很大程度上取决于游离细菌：游离细菌既是聚集体的定殖池，也会被模拟的牡蛎直接捕获。聚集体的浓度同样具有重要影响，但其作用效果取决于游离细菌的浓度。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负面的影响。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类软体动物对致病细菌的摄取，并揭示了细菌物种附着于聚集体的倾向，是理解物种特异性积累过程的关键因素。