Community and single cell analyses reveal complex predatory interactions between bacteria in high diversity systems

Studying the role of predator-prey interactions in food-web stability and species coexistence in the environment is arduous. Here, Cohen et al. use a combination of community and single-cell analyses to show that bacterial predators can regulate prey populations in the species-rich environments of wastewater treatment plants. 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.

Automated summary

Research shows that bacterial predators in wastewater treatment plants can regulate prey populations in a density-dependent manner, leading to stable total population numbers. Predatory landscapes oscillate at different temporal scales, affecting both abundant and rarer prey populations, while the coexistence of numerous predators is explained through niche partitioning based on differential prey range. This study's approach using single-cell sorting and community sequencing could be applied to decipher community interactions in other systems.