ACETATE AND CARBON-DIOXIDE ASSIMILATION BY DESULFOVIBRIO-VULGARIS (MARBURG), GROWING ON HYDROGEN AND SULFATE AS SOLE ENERGY-SOURCE

Desulfovibrio vulgaris (Marburg) was grown on hydrogen plus sulfate as sole energy source and acetate plus CO2 as the sole carbon sources. The incorporation of U-14C acetate into alanine, aspartate, glutamate, and ribose was studied. The labelling data show that alanine is synthesized from one acetate (C-2 + C-3) and one CO2 (C-1), aspartate from one acetate (C-2 + C-3) and two CO2 (C-1 + C-4), glutamate from two acetate (C-1-C-4) and one CO2 (C-5), and ribose from 1.8 acetate and 1.4 CO2. These findings indicate that in Desulfovibrio vulgaris (Marburg) pyruvate is formed via reductive carboxylation of acetyl-CoA, oxaloacetate via carboxylation of pyruvate or phosphoenol pyruvate, and α-ketoglutarate from oxaloacetate plus acetyl-CoA via citrate and isocitrate. Since C-5 of glutamate is derived from CO2, citrate must have been formed via a (R)-citrate synthase rather than a(S)-citrate synthase. The synthesis of ribose from 1.8 mol of acetate and 1.4 mol of CO2 excludes the operation of the Calvin cycle in this chemolithotrophically growing bacterium. © 1979 Springer-Verlag.