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BdellovibrioBdellovibrio is a genus of Gram-negative, obligate aerobic bacteria. One of the more notable characteristics of this genus is that members parasitize other gram-negative bacteria by entering into their periplasmic space and feeding on the biopolymers, e.g. proteins and nucleic acids, of their hosts. After entering the periplasmic space of its host the Bdellovibrio bacterium forms a structure called bdelloplast, which consists of both predator and prey. The predator cell can remain dormant at this stage, without affecting the viability of the host. In most cases, though, Bdellovibrio moves on and devours its prey. 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-shaped motile rod that is about 0.3-0.5 by 0.5-1.4 m in size with a barely discernible flagellum. Colonies of Bdellovibrio show up as a growing clear plaque in an E. coli lawn. Another notable feature of Bdellovibrio is the sheath that covers its flagellum. This is a rare characteristic among bacteria. This flagellum is lost when Bdellovibrio penetrates its prey. Bdellovibrio attacks other gram-negative bacteria by colliding with them at a relatively blazing speed of 100 m per second, which is about 100 times its size. It enters into their periplasmic space within about 10 minutes by using hydrolytic enzymes. After draining the host of nutrients, it becomes a spherical bdelloplast, then elongates, and divides into several smaller complete Bdellovibrios. At the completion of its life cycle, which takes from one to three hours, the Bdellovibrio burst free from the remainder of the host cell in order to attack new preys. Bdellovibrio bacteriovorus was first described by Stolp and Starr in 1963. Two other species, B. starrii and B. stolpii, have been moved to a separate genus Bacteriovorax.
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