Nitrogen fixation by photosynthetic bacteria : (Rhodospirilum rubrum, Rhodopseudomonas capsulata, glutamine ,nitrogenase)
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Biological nitrogen fixation is not only essential for world nitrogen balance but it is also an alternative to expensive commercial fertilizer for crop production. To achieve the maximum utilization of this natural process, an understanding of the mechanism of N[subscript 2] reduction and its regulation is being sought. The photosynthetic bacteria, in particular members of the Rhodospirillaceae, are attractive organisms for genetic and biochemical analyses of nitrogen fixation. Characterization of mutants of these bacteria derepressed for synthesis of the nitrogenase complex in the presence of ammonium salts supports a critical role for glutamine and [lowercase alpha]-ketoglutarate in the regulation of synthesis. In addition, a mechanism exists for activity control by covalent modification of one of the protein components of the complex. The signal for modification and the extent to which this control mechanism occurs in other diazotrophs are under investigation.