THE INFLUENCE OF AMINO ACIDS AND PROTEINS ON NITROGEN FIXATION BY AZOTOBACTER CHROOCOCCUM

Abstract

A. chroococcum was grown in a synthetic medium to which various quantities of the following amino acids and proteins were added: d-lycine, dl-isolucine, dl-valine, iso-valine, l-aspartic acid, glutamic acid, dl-lysine, d-arginine, dl-methionine, cystine, tyrosine, phenylalanine, l-tryptophane, hydroxyproline, l-histidine, l-proline, casein, albumin, and gelatin; and its N-fixing powers were detd. Tyrosine, dl-isolucine, hydroxyproline, and l-histidine greatly increased N fixation by A. chroococcum. Phenylalanine and d-arginine were the only 2 amino acids used which materially retarded N fixation by A. chroococcum. The other amino acids tested either slightly increased fixation or were without effect. Cystine and dl-methionine increased N fixation approximately 20%, and their actions paralleled each other throughout the concs. tested. Phenylalanine is the only amino acid tested which may occur in soils in sufficient concs. to retard N fixation by A. chroococcum. Casein and albumin materially increased N fixation by Azotobacter; gelatin greatly retarded it.