Carbon assimilation pathways in sulfate reducing bacteria. Formate, carbon dioxide, carbon monoxide, and acetate assimilation by Desulfovibrio baarsii

The capacity to synthesize an acetate unit from two C1-compounds obviously distinguishes D. baarsii from those Desulfovibrio species, which require acetate as a carbon source in addition to CO2.

Abstract

Desulfovibrio baarsii is a sulfate reducing bacterium, which can grown on formate plus sulfate as sole energy source and formate and CO2 as sole carbon sources. It is shown by 14C labelling studies that more than 60% of the cell carbon is derived from CO2 and the rest from formate. The cells thus grow autotrophically. Labelling studies with [14C]acetate, 14CO and [14C]formate indicate that CO2 fixation does not proceed via the Calvin cycle. The labelling patterns of alanine, aspartate, glutamate, and glucosamine indicate that acetate (or activated acetic acid) is an early intermediate in formate and CO2 assimilation; the methyl group of acetate is derived from formate, and the carboxyl group from CO2 via CO; pyruvate is formed from acetyl-CoA by reductive carboxylation. The capacity to synthesize an acetate unit from two C1-compounds obviously distinguishes D. baarsii from those Desulfovibrio species, which require acetate as a carbon source in addition to CO2.