Studies on the metabolism of mould fungi

Abstract

Acid-producing molds are unable to grow unless small amts. of phosphate are present in the nutrient medium. Mycelia of Aspergillus niger grown in the presence of large concs. of phosphate develop more rapidly than those grown in low cones. They have a higher N metabolism and exhibit a substantially increased content of certain vitamins (17 [gamma] aneurin, 72 [gamma] riboflaviri and 270 7 nicotinic acid per gm.). The uptake of phosphate by acid-producing mycelia depends on the presence of oxygen. The absorbed phosphate is converted into acid-hydrolyzable compounds. The formation of these compounds in the mycelium reaches its peak at the preconidial stage. During autolysis they are decomposed and excreted into the medium as orthophos-phate. Their breakdown is made possible by the occurrence of a phosphatase in the mycelium as well as in the medium. The enzyme is highly active towards metaphosphate, pyrophosphate, phosphoglycerol, phosphoglycerate, phosphohexo-ses, adenine nucleotides, aneurine disphosphate and phy-tate. The outstanding property of this polyphosphatase is the ease with which it acts on metaphosphate. It may, therefore, be referred to as a metaphosphatase. The enzyme has been purified. There exists an intimate relationship between the P metabolism, the carbohydrate metabolism and the respiration of molds. Cyanide, azide, iodoacetate and fluoride inhibit the mold respiration and bring the carbohydrate oxidation as well as the phosphate absorption to a standstill. This relationship was studied on mycelia grown directly in the cups of Barcroft differential manometers.