Isolation and characterization of a desulforubidin-containing sulfate-reducing bacterium growing with glycolate

Sulfate-dependent degradation of glycolate was studied with a new sulfate-reducing bacterium, strain PerGlyS, enriched and isolated from marine anoxic sediment. Cells were gram-negative, motile rods with a DNA G+C content of 56.2±0.2 mol%. Cytochromes of theb- andc-type and menaquinone-5 were detected. A sulfite reductase of the desulforubidin-type was identified by characteristic absorption maxima at 279, 396, 545, and 580 nm. The purified desulforubidin is a heteropolymer consisting of three subunits with molecular masses of 42.5 (α), 38.5 (β), and 13 kDa (γ). Strain PerGlyS oxidized glycolate completely to CO₂. Lactate, malate, and fumarate were oxidized incompletely, yielding more sulfide and less acetate than expected for typical incomplete oxidation of these substrates. Part of the acetate residues formed was oxidized through the CO-dehydrogenase pathway. The biochemistry of glycolate degradation was investigated in cell-free extracts. A membrane-bound glycolate dehydrogenase, but no glyoxylate-metabolizing enzyme activity was detected; the further degradation pathway is unclear. Dedicated to Prof. Norbert Pfennig on the occasion of his 70th birthday