Nitrate utilization and growth in biotin-deficient Aspergillus nidulans.

A marked increase in the cellular synthesis accompanied by a decrease in the total fatty acid content was observed when Aspergillus nidulans was grown on NH4NO3 as a sole nitrogen source, in the medium containing avidin. Because of the increased uptake of NH4(plus), the level of NH4(plus), was lowered in the medium; as a result there is early uptake and assimilation of nitrate by a biotin-deficient culture as compared with the normal culture of A. nidulans. At about 17mM concentration, NH4(plus) repressed the activity of nitrate reductase. The regulation of NO3(minus) uptake and its assimilation with respect to the growth of A. nidulans have been discussed.