Predatory Bdellovibrio bacteriovorus are natural antimicrobial organisms, killing other bacteria by whole-cell invasion. Self-protection against prey-metabolizing enzymes is important for the evolution of predation.

Initial prey entry involves the predator’s peptidoglycan DD-endopeptidases, which decrosslink cell walls and prevent wasteful entry by a second predator. Researchers identify and characterize a self-protection protein from B. bacteriovorus, Bd3460, which displays an ankyrin-based fold common to intracellular pathogens of eukaryotes.

Co-crystal structures reveal Bd3460 complexation of dual targets, binding a conserved epitope of each of the Bd3459 and Bd0816 endopeptidases.

Complexation inhibits endopeptidase activity and cell wall decrosslinking in vitro. Self-protection is vital — ΔBd3460 Bdellovibrio  deleteriously decrosslink self-peptidoglycan upon invasion, adopt a round morphology, and lose predatory capacity and cellular integrity.

Their analysis provides the first mechanistic examination of self-protection in Bdellovibrio, documents protection-multiplicity for products of two different genomic loci, and reveals an important evolutionary adaptation to an invasive predatory bacterial lifestyle.

http://www.nature.com/ncomms/2015/151202/ncomms9884/full/ncomms9884.html