Comparison of Predatory Phenotypes and Genotypes Between Bdellovibrio sp. BIS2 and Bacteriovorax sp. HI3 Isolated...

Bdellovibrio and like organisms (BALOs) are predatory bacteria, which play crucial roles in shaping community structure and maintaining diversity in microbial ecosystems. However, functional and genetic variation among coexisting BALOs remains largely unexplored. Here, we characterised Bdellovibrio sp. BIS2 and Bacteriovorax sp. HI3, which were isolated from the same freshwater environment at different time points. Predation assays and a functional genomic analysis revealed that the predators have distinct prey ranges and predatory behaviours with associated genotypic differences, which may contribute to niche partitioning in the shared habitat. BIS2 possessed an extensive set of flagellar genes, likely contributing to its higher motility and rapid spatial exploration. However, cell debris remained after predation because the prey cells were incompletely lysed. HI3 displayed efficient localised predation and thorough lysis of prey cellular components. The difference in predation efficiency was likely attributed to distinct profiles of hydrolytic enzymes in the two BALOs, including enzymes critical for prey cell lysis and exit from the prey. Genomic regions unique to each predator with predation-associated genes suggest that genetic divergence drove the evolution of specialised predatory properties across BALOs. These findings provide insights into variation in predatory traits among BALOs, a key mechanism enabling coexistence and adaptation.