NUTRITIONAL STUDIES ON THE GENUS HIRSUTELLA: II. NITROGEN UTILIZATION IN A SYNTHETIC MEDIUM

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Abstract
The growth responses of Hirsutella gigantea to different nitrogen sources were studied. Experiments showed that the mycelium hydrolyzate contained at least 14 of the amino acids, that the fungus was unable to utilize inorganic nitrogenous compounds, that ammonium tartrate was inferior to amino-nitrogen, and that the L or DL isomers of the different amino acids induced better growth than did the D form.The 10 most suitable nitrogen sources in order of decreasing growth were: L-glutamic acid, L-tyrosine, ammonium tartrate, DL-aspartic acid, L-proline, L-arginine, L-leucine, DL-α-alanine, DL-serine, and DL-histidine. The total yield, however, obtained in a synthetic medium with each of these substances was shown to be directly dependent upon the quantity of inoculum used. The enhanced growth resulting from the addition of increased inoculum is ascribed to accessory growth factors carried over with the mycelial fragments despite six washings in saline.The maximum growth of H. gigantea developed in a dextrose–salts medium containing L-glutamic acid as a source of nitrogen, and yeast extract, inoculum filtrate, and liver fraction "L" as a source of growth factors.The lack of uniformity associated with nutritional studies conducted in chemically defined media has been briefly mentioned.