1982 Volume 28 Issue 5 Pages 359-368
The nitrogenase enzyme activity of free-living, microaerobically grown Rhizobium japonicum 61A76, USDA 83 and Rhizobium sp. 32H1 was depressed by ammonia, several individual amino acids and complex nutrients like casamino acids and yeast extract when added to cultures growing on glutamate or aspartate. The extent of depression of nitrogenase activity by these nitrogen-containing compounds was concentration-dependent but varied with the Rhizobium strain. Higher depression of activity with ammonia was noted in strains which had better uptake of ammonia under the microaerobic conditions that are essential for nitrogenase synthesis in rhizobia.