Bdellovibrio bacteriovorus is an obligate predatory bacterium that hunts other Gram-negative bacteria with extraordinary speed and mechanical precision. Swimming at velocities up to 160 cell lengths per second via a single polar flagellum, Bdellovibrio collides head-first with its prey. Upon contact, the predator sheds its flagellum and attaches tightly using specialized type IV pili.
It then initiates a mechanical and enzymatic breach of the host outer membrane and peptidoglycan cell wall. Bdellovibrio secretes a cocktail of hydrolytic enzymes, including glycanases, endopeptidases, and deacetylases, which target specific cross-links in the host's peptidoglycan layer. Crucially, the predator modifies the host cell wall rather than destroying it completely: by deacetylating peptidoglycan strands, it softens the structure to allow passage while reinforcing the wall against full osmotic lysis.
Bdellovibrio squeezes through a tiny port into the host's periplasmic space—the narrow region between the outer and inner membranes. Once inside, Bdellovibrio reseals the outer membrane pore and remodels the host cell into a spherical protective chamber called a bdelloplast. Safe inside the periplasm, the predator releases digestive enzymes into the host cytoplasm, consuming its macromolecules to grow into a long filament.
Once nutrients are exhausted, the filament septates into multiple flagellated progeny, which produce lytic enzymes to break open the bdelloplast shell and swim away to hunt new hosts.