A fundamental question in community ecology is the role of predator–prey interactions in food-web stability and species coexistence. Although microbial microcosms offer powerful systems to investigate it, interrogating the environment is much more arduous. Here, we show in a 1-year survey that the obligate predators Bdellovibrio and like organisms (BALOs) can regulate prey populations, possibly in a density-dependent manner, in the naturally complex, species-rich environments of wastewater treatment plants. Abundant as well as rarer prey populations are affected, leading to an oscillating predatory landscape shifting at various temporal scales in which the total population remains stable. Shifts, along with differential prey range, explain co-existence of the numerous predators through niche partitioning. We validate these sequence-based findings using single-cell sorting combined with fluorescent hybridization and community sequencing. Our approach should be applicable for deciphering community interactions in other systems.

群落生态学的一个基本问题是捕食者与猎物之间的相互作用在食物网稳定性和物种共存中的作用。尽管微生物微观世界提供了强大的系统来研究它，但探究环境却要困难得多。在这里，我们在一项为期一年的调查中表明，专性捕食者蛭弧菌和类似生物（BALO）可以在污水处理厂自然复杂、物种丰富的环境中以密度依赖的方式调节猎物种群。丰富和稀有的猎物种群都会受到影响，导致捕食景观在不同时间尺度上发生振荡变化，而总种群数量保持稳定。变化以及不同的猎物范围解释了众多捕食者通过生态位划分的共存。我们使用单细胞分选结合荧光杂交和群落测序来验证这些基于序列的发现。我们的方法应该适用于破译其他系统中的社区交互。