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（Bivalves）会过滤大量水体，因此会在体内积累细菌，其中包括潜在的人类致病菌（如弧菌（vibrios））。当这些细菌自由悬浮于水柱中时，捕获效率较低；但它们也会附着于海洋凝聚物（marine aggregates）上，而双壳类对附着了细菌的凝聚物的捕获效率接近100%。基于此，加之海洋凝聚物通常富含异养细菌，学界此前提出假说：海洋凝聚物是细菌向双壳类体内转运的重要载体。然而，凝聚物与游离细菌对双壳类体内该类细菌积累的相对贡献尚不明确。本研究构建了基于智能体的模型（agent-based model），以模拟牡蛎体内弧菌类细菌的积累过程。模拟设置了符合实际场景的细菌与凝聚物浓度范围，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：附着于凝聚物的细菌的贡献程度，高度依赖于游离细菌——游离细菌既是凝聚物的定殖菌群来源，同时也会被模拟牡蛎直接捕获。凝聚物的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，凝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，凝聚物对细菌积累的影响可忽略不计，甚至会产生轻微的负面作用。本研究结果首次证明，海洋凝聚物的浓度会影响双壳类对致病细菌的摄取；同时也表明，细菌物种保留附着于凝聚物的能力，是理解物种特异性细菌积累机制的关键因素。