Some energy-producing systems in Bdellovibrio bacteriovorus, strain 6-5-S

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Abstract
Bdellovibrio bacteriovorus 6-5-S, an obligate bacterial parasite, was grown on cells of Spirillum serpens in 20 lL of medium. Maximum numbers of the parasite were attained at 42-55 hr about 2 -12 hr after there were no viable host cells remaining. Growth of B. bacteriovorus occurred only under aerobic conditions. The organism is rich in catalase. Endogenous respiration of cells and oxidation of NADH by cell extracts is inhibited by cyanide and azide but not by CO. Difference spectra indicate the parasite has a cytochrome system and probably couples oxidation to phosphorylation, although efforts to demonstrate fixation of inorganic 32P into organic phosphate failed. Glutamine, glutamate, and asparagine stimulate respiration, and cell extracts contain glutamate and alanine dehydrogenase. The B. bacteriovorus 6-5-S also has a tricarboxylic acid cycle, as isocitric dehydrogenase, the a-ketoglutarate dehydrogenase system, succinyl-CoA synthetase, fumarase and malate dehydrogenase were found in the soluble fraction of the cell extract, and a bound succinic dehydrogenase in the particulate fraction. The glyoxylate cycle may not be present since isocitric lyase could not be detected despite the presence of acetate in the growth medium. Tests on cell extracts for glucose kinase, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were also negative. However, aldolase, glyceraldehyde 3-phosphate dehydrogenase, pyruvate kinase and lactic acid dehydrogenase were present although at rather low levels, indicating that the parasite can obtain energy from the substrate-linked phos-phorylations of the glycolytic system.