Biochemical Studies on Sulfate-reducing Bacteria

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Abstract
1) Sulfite reductase was purified to an ultracentrifugally and disc-electrophoretically homogeneous state from a dissimilatory sulfate-reducer, Desul fovibrio vulgaris. 2) The purified enzyme had an absorption spectrum identical with that of a green pigment, desulfoviridine, showing absorption maxima at 630, 585, 410, 390, and 280 mμ. The spectrum was not affected by sodium dithionite. Similarities in the spectrum and the behavior during purification indicate the identity of the enzyme with desul-foviridin. 3) From the results of sodium dodecylsulfate-polyacrylamide gel electrophoresis, it was shown that the enzyme was composed of at least two species of polypeptide chains having molecular weights of about 45,000 and 55,000. 4) When coupled with the hydrogenase-methylviologen system, the purified enzyme formed trithionate as well as thiosulfate and hydrogen sulfide from sulfite with the consumption of molecular hydrogen. 5) The pathway of sulfite reduction and the participation of trithionate and thiosulfate reductases in the sulfite-reducing system of sulfate-reducing bacteria, leading to the formation of sulfide, are discussed.

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