Formic Hydrogenlyase and the Photoassimilation of Formate by a Strain of Rhodopseudomonas palustris

Abstract

A photosynthetic bacterium isolated by enrichment on media containing formate as major source of cell carbon was identified as a strain of Rhodopseudomonas palustris . It grew on a wide range of simple organic compounds including alcohols, fatty acids, and hydroxyacids, on a chemically defined medium with biotin and p -aminobenzoic acid as essential growth factors. The organism grew on formate or photoautotrophically with molecular hydrogen or thiosulfate only in the presence of yeast extract. Ability to photoassimilate formate could be shown only in organisms grown in the presence of formate. The organism contained an inducible formic hydrogenlyase consisting of a soluble formic dehydrogenase, a particulate hydrogenase, and one or more intermediate, but as yet unidentified, electron carriers. The formic hydrogenlyase could be reconstituted from a particulate hydrogenase and a partially purified soluble formic dehydrogenase. Some properties of the formic dehydrogenase and hydrogenase have been compared with that of the formic hydrogenlyase system.