Bdellovibrio

Bdellovibrio is a genus of gram-negative, obligate aerobic bacteria. One of the most notable characteristics of this genus is that members can prey upon other gram-negative bacteria and feed on the biopolymers, e.g. proteins and nucleic acids, of their hosts. They have two lifestyles: a host-dependent, highly mobile phase, the "attack phase", in which they form "bdelloplasts" in their host bacteria; and a slow-growing, irregularly shaped, host-independent form.

==Bdellovibrio bacteriovorus== The best studied of these is Bdellovibrio bacteriovorus, which is found almost exclusively in host dependent growth in nature. In this free swimming attack form after searching for prey using its pili, it burrows through the host outer membrane/ peptidoglycan cell wall and enters the periplasmic space. The Bdellovibrio bacterium then forms a structure called a bdelloplast. This bdelloplast is created as the host cell is modified to become spherical in shape. Inside the bdelloplast, the singular large flagellum of the predatory Bdellovibrio is lost. The host cell is then rapidly killed allowing the passage of molecules from the interior of the host cytoplasm through to the periplasm freely, and the periplasm dwelling Bdellovibrio to feed. Using some of these molecules the Bdellovibrio creates a protective environment by reinforcing the peptidoglycan cell wall of the host in which it now dwells using amidases and transpeptidases. After around 4hrs, depending on ambient temperature, the Bdellovibrio has increased in size dramatically through this nourishment. It divides to replicate and then leaves via final lysis of the host's cell wall and membranes. The newly emerging Bdellovibrio uses their newly grown powerful flagella to swim away and find the next suitable host. Because of this intermittent bdelloplast stage, and momentary parasitic phase (15-20 mins), Bdellovibrio could be considered bacterial predators or parasites.