Lithoautotrophic growth of the freshwater strain Beggiatoa D-402 and energy conservation in a homogeneous culture under microoxic conditions

The freshwater filamentous bacterium Beggiatoa D-402 was shown to grow lith o auto trophically in a homogeneous culture under microoxic conditions only , the growth yield being the highest at 0.1 Mg O-2 l(-1). High activities o f the Calvin cycle key enzymes and of the dissimilatory path thiosulfate ox idation enzymes were found in the bacterial cells. The rate Of CO2 fixation above 112 nmol min(-1) (mg protein)(-1), an about 90% increase in the prot ein carbon at the expense of CO2 carbon and an increase in the molar yield up to 12 mg dry weight (mmol oxidized thiosulfate)(-1) indicate the bacteri al growth was autotrophic. Thiosulfate, was oxidized by the strain almost c ompletely into sulfate. The metabolically useful energy was conserved by ox idative phosphorylation that was coupled to oxidation of sulfur compounds. The bacterial membranes were found to contain CO-binding cytochromes b and two cytochromes c with M-r 23 and 26 kDa, the terminal part of the respirat ory chain containing presumably a cbb(3)-type oxidase. A cytochrome c with M-t 12 kDa was detected in the soluble fraction. (C) 2001 Federation of Eur opean Microbiological Societies. Published by Elsevier Science B.V. All rig hts reserved.