ENERGY COUPLING IN DESULFOVIBRIO DESULFURICANS

Abstract

D. desulfuricans Hildenborough strain, growing in a putatively autotrophic environment containing H2, bicarbonate, and yeast extract, forms most of its cell C from yeast extract. The bicarbonate provides no more of the cell C than it provides under heterotrophic conditions with ethanol as the C source. In the absence of H2, little or no growth occurs on yeast extract; in strictly autotrophic medium without yeast extract growth also is marginal. The organism oxidizes isobutanol but cannot use it as a C source. In an isobutanol-yeast extract medium, isobutanol functions as does H2 by providing the energy for growth on components of the yeast extract. It is concluded that D. desulfuricans has a hitherto unreported type uf metabolism, the energy for cell synthesis being derived from an inorganic molecule or from a nonassimilable organic molecule, and cell C being derived from organic molecules which are unable to act as energy sources. These findings are discussed in relation to certain general problems of autotrophy, to hydrogen oxidation by heterotrophic bacteria, and to autotrophy in sulfate-reducers.