PYRUVATE METABOLISM, CARBON DIOXIDE ASSIMILATION, AND NITROGEN FIXATION BY AN ACHROMOBACTER SPECIES.

Hamilton, I. R. (University of Wisconsin, Madison), R. H. Burris, P. W. Wilson, and C. H. Wang. Pyruvate metabolism and carbon dioxide assimilation by an Achromobacter species. J. Bacteriol. 89:647-653. 1965.-Carbon dioxide fixation by washed whole cells of Achromobacter N4-B has been observed during anaerobic pyruvate metabolism with both nitrogen- and NH(4) (+)-grown cells. Labeled sodium bicarbonate-C(14) was assimilated into cells by a mechanism requiring pyruvate under conditions of nitrogen fixation, nitrogenase induction, and assimilation of NH(4) (+). Of the assimilated radioactivity, 89% appeared in six amino acids and two ninhydrin-positive unknown compounds, with the distribution of the label essentially independent of the nitrogen nutritional state of the organism. Aspartic and glutamic acids were the most highly labeled, with lesser amounts in glycine, alanine, ornithine, arginine, and the unknowns. All of the radioactivity extracted from these cells by ethanol-boiling water appeared in a protein fraction precipitated by 20% trichloroacetic acid. Radiorespirometric experiments with individually labeled pyruvate substrates demonstrated the preferential decarboxylation of the C-1 of pyruvate by this organism in a flowing helium gas phase. This decarboxylation was almost completely inhibited by using flowing nitrogen in place of helium; the addition of 0.5% CO(2) to the flowing nitrogen prevented inhibition and allowed 70% of the expected CO(2) evolution. These results, coupled with those from growth experiments, indicate a carbon dioxide requirement for anaerobic growth and pyruvate metabolism, which appears to be coupled to the formation of protein precursors.