Bdellovibrio is a genus of Gram-negative, obligate aerobic bacteria.

One of its more notable characteristics of this genus is that members parasitize other gram-negative bacteria by entering into their periplasmic space and feeding on the cytoplasmic fluid of it's host. When the host dies, a Bdellovibrio bacterium becomes a bdelloplast, elongates, and then divides.

Bdellovibrio species are found in river water or soil and live an intraperiplasmic existence. To enrich for Bdellovibrio use NB/500 (nutrient broth at 1:500 dilution) and mix with hot soft agar with E. coli at 30C for one week.

Under the microscope, a Bdellovibrio appears as a comma-shapped motile rod that is about 0.3 by 1.5 in size with a barely discernible flagellum. Colonies of Bdellovibrio show up as a growing clear plaque in an E. coli lawn.

Bdellovibrio attack other gram-negative bacteria, enter into their periplasmic space, drain the host of nutrients, becomes a spherical bdelloplast, then elongates, and divides.