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 CO as the sole carbon sources. The incorporation of U-C 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 CO (C-1), aspartate from one acetate (C-2 + C-3) and two CO (C-1 + C-4), glutamate from two acetate (C-1−C-4) and one CO (C-5), and ribose from 1.8 acetate and 1.4 CO. 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 CO, 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 CO excludes the operation of the Calvin cycle in this chemolithotrophically growing bacterium. [ABSTRACT FROM AUTHOR]