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SUMMARY: Asexual sporulation of Aspergillus niger occurred in submerged culture in a liquid minimal medium without added nitrogen, in low ammonium-N concentrations, and in a wide range of nitrate-N concentrations. Ammonium salts containing more than 48 mg. atom N/l. were inhibitory to conidiation. Most amino acids overcame the ammonium inhibition of conidiation when added to an ammonium nitrate medium. Glyoxylate and several intermediates of the tricarboxylic acid (TCA) cycle also promoted conidiation in the presence of ammonium. Changes in the medium of conidiating and non-conidiating cultures were examined with respect to nitrogen and glucose concentrations, dry weight and pH value. The activities of two glutamate dehydrogenases, one requiring NAD and the other specific for NADP, and of aspartate and alanine amino transferases varied during growth as a function of the stage of the life cycle and of the growth medium. There was no clear correlation between the activities of these enzymes and conidiation of this fungus.
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