Regulation of Nitrate Reductase in Chlorella vulgaris

Studies of Syrett and Morris on the utilization of nitrate and ammonium by Chlorella have shown that ammonium is assimilated preferentially (14). These investigators also demonstrate that the level of nitrate reductase is increased by adding nitrate and decreased by adding ammonium to Chlorella cultures (7). However, since these studies suggested that a product of ammonium assimilation rather than ammonium per se was responsible for decreasing the nitrate reductase increase, a number of amino acids (as products of ammonium metabolism) were tested as possible inhibitors.