Harnessing predation : the probiotic and antibiotic potential of Bdellovibrio
Predatory bacteria like Bdellovibrio and like organisms (BALOs) are widespread in aquatic and host-associated ecosystems, preying on Gram-negative bacteria. Despite over 60 years of research, their ecological diversity, predation mechanisms, and long-term microbiome roles remain underexplored. Their ability to reduce pathogens and shape microbial communities positions them as promising “living antibiotics.” Chapter 1 explored nine newly isolated host-associated BALOs from the Pseudobdellovibrionaceae family using genomic and microscopy analyses. Several novel Bdellovibrio species and two new genera were identified. Comparative genomics of 250+ core genes supported periplasmic predation as ancestral. Epibiotic strains lacked genes for host-independent growth, indicating that they were obligate predators due to genomic trade-offs. Chapter 2 assessed BALO probiotic potential in C. elegans using two strains: B. krueschi MYbb4 (narrow prey range) and B. tiberii MYbb2 (broad range). Introduced into CeMbio(12) and CeMbio(43) communities, both altered microbiome composition. MYbb4 caused distinct taxonomic shifts; MYbb2 enriched Ochrobactrum. These shifts extended lifespan in low-complexity, nutrient-rich settings. LC-MS and reporter assays confirmed microbial B12 production. Supplementation experiments showed B12 modulates host fertility and lifespan. Chapter 3 developed a three-step assay for antimicrobial resistance in plaque-forming BALOs. Applied to B. bacteriovorus HD100 and B. tiberii MYbb2, it revealed consistent MICs and species-specific profiles: resistance to ciprofloxacin and susceptibility to piperacillin/tazobactam. This offers a reproducible method for BALO-antibiotic combination testing. Together, these findings link BALO genomic diversity to ecological function and therapeutic potential.
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