Nitrogen fixation and photoproduction of molecular hydrogen by Thiorhodaceae

Summary Nitrogen fixation has been shown to be a characteristic of two previously untested strains of the purple sulfur bacteriumChromatium sp.Chromatium strains have been shown to produce molecular hydrogen when suppliedD-L malate and bicarbonate in the presence of light and the absence of exogenous ammonia and molecular nitrogen. These results are discussed in relation to current findings on the nitrogen metabolism of the photosynthetic bacteria. Supported in part by grants from the Rockefeller Foundation, the Atomic Energy Commission, and the Research Committee of the Graduate School from funds provided by the Wisconsin Alumni Research Foundation.