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）会滤食大量水体，进而在体内积累细菌，其中包括潜在人类致病菌，例如弧菌（vibrios）。这些游离于水柱中的细菌被双壳贝类捕获的效率较低，但它们还会附着在海洋团聚物（marine aggregates）上，而双壳贝类对附着于此类团聚物的细菌的捕获效率接近100%。基于此，加之海洋团聚物通常富含异养细菌（heterotrophic bacteria），学界此前提出假说：海洋团聚物是细菌向双壳贝类体内转移的重要载体。然而，团聚物与游离细菌对双壳贝类体内此类细菌积累的相对贡献仍不明确。本研究构建了基于智能体模型（agent-based model）以模拟牡蛎（oysters）体内弧菌类细菌的积累过程。模拟实验在符合自然实际的细菌与团聚物浓度范围内开展，并纳入了伪粪（pseudofeces）产生量对颗粒物的依赖关系。模型结果显示，附着于团聚物的细菌的贡献程度很大程度上取决于游离细菌：游离细菌既是团聚物的定殖源，同时也可被模拟牡蛎直接捕获。团聚物浓度同样会产生影响，但其作用效果取决于游离细菌的浓度。当细菌总浓度较高时，团聚物携带的细菌会成为牡蛎体内细菌的主要来源。当游离细菌浓度较低时，团聚物对细菌积累仅存在中性影响，甚至会产生轻微的负面作用。本研究结果首次提供证据表明，团聚物浓度可影响双壳贝类对致病菌的摄取，并揭示了细菌物种附着于团聚物的倾向性是理解物种特异性细菌积累的关键因素。