Liquid Cultures

The intracellular life cycle of Bdellovibrio bacteriovorus 109 growing on Escherichia coli in a dilute nutrient medium exhibits a period of constant infective titer while the parasite grows and elongates inside the host cell. This period is terminated after 2 to 4 hr, and the number of the plaque-forming units in the culture rises rapidly to as much as six times the initial titer. The growth pattern of Bdellovibrio is similar with actively growing or resting host cells, or with host cells killed by ultraviolet irradiation or by heating at 70 C. The yield of B. bacteriovorus strain 109 in twomembered cultures with E. coli B depends on the host concentration and may reach 7.5 x 1010 cells per ml. Penicillin, which has no effect on the attachment and penetration of Bdellovibrio, inhibits its multiplication.