Characterization of bdellocysts of Bdellovibrio sp.

Bdellovibrio sp. strain W will infect and produce resting cells, termed bdellocysts, in a variety of gram-negative bacteria. Bdellocysts appeared to be produced only within susceptible prey and never in their absence. Optimum conditions for encystment included infection of stationary-phase prey cells in 0.05 M potassium phosphate buffer (pH 7.5) at concentrations of prey and bdellovibrios of 2 X 10(9) cells per ml with a multiplicity of infection of unity. Bdellocysts contained more deoxyribonucleic acid, ribonucleic acid, protein, and carbohydrate per cell than did vegetative cells. Poly-beta-hydroxybutyrate and dipicolinic acid were not detected. Bdellocysts were more resistant than vegetative cells to effects of elevated temperatures, sonic treatment, and desiccation. Bdellocysts remained viable for extended periods when incubated in the absence of prey, whereas vegetative cells lost viability rapidly under the same conditions. Their survival under starvation conditions may be due to the low rate of endogenous respiration by the bdellocysts. Bdellocysts are capable of germination in the presence or absence of prey cells in rich medium such as peptone-yeast extract.