Gram negative, motile, uniflagellated aerobic bacteria; distinctive in its predatory behavior: Bdellovibrios attack other Gram negative cells, penetrate their periplasm, multiply in their cytoplasm, and finally burst their cell envelopes to start anew. Although many predator bacteria may lyse other bacteria, and many "micropredators" have been described, these Bdellovibrio-like organisms can grow without bacterial prey, and do not divide inside the periplasm. Two life forms.