Enrichment isolation and metabolic characteristics of Halobacteriovorax, cosmopolitan obligate predators in marine conditions

Bdellovibrionota, ubiquitous obligate predators regulating microbial ecosystems, suffer cultivability limitations with only 12 known isolates despite >1,120 genomes. We developed a prey-addition enrichment system and isolated 33 marine Halobacteriovorax strains from sediments that fall into four species, three of which are candidate novel species. Genomic analyses revealed streamlined metabolism with auxotrophy for amino acid/hypoxanthine synthesis, enhanced chemotaxis, and specialized CAZymes (e.g., GH23 hydrolases), defining adaptations for obligate predation. Predation assays demonstrated broad activity against aquaculture pathogens (Vibrionaceae/Alteromonadales), optimal at 10² predator: prey ratios. In simulated seawater, isolates achieved 3-log reduction of Vibrio alginolyticus within 10 hours, highlighting potent biocontrol utility. This work bridges cultivability gaps via ecological strategies, advancing evolutionary insights into predation mechanisms while positioning Bdellovibrionota as precision biocontrol agents for sustainable aquaculture disease management.