Sucrose consumption by the wild-type Neurospora crassa is quicker, with much more ethanol produced, in the ammonium medium than in nitrate as single N source. On low sugar concentration which is quickly nullified, little alcohol is produced and early conidiation can develop. The higher the initial sugar concentration, the higher is the alcoholigenic coefficient defined as the efficiency of alcoholic glycolysis per unit of sugar consumed, and the more complete is the conidial "repression" in ammonium medium. The nitrate counteracts this catabolic repression effect and, depressing the alcoholigenic coefficients, permits conidiation even on high sugar (8 %) medium. The "fluffy" mutant produces relatively less ethanol (average 2-3 times less) in all cases even though it increases its alcoholigenic coefficient with the increased sugar concentration. Surprisingly, it is not induced to alcoholigenic glycolytic disinhibition by ammonium and produces even more alcohol in nitrate than in ammonium media, thus revealing an inability to benefit from the antiglycolytic, normally conidiogenous, effect of nitrate. Suggestion is made that this amacroconidial mutant is defective in its metabolic regulation related to the Pasteur effect which is required for conidiogenic expression in the wild type.

Cell Differentiation↗

PubMedDate not supplied

[Studies on the conidial differentiation of "Neurospora crassa" VI.--Functional anomalies of the conditional aconidial mutant "amycelial" (author's transl)].

Studies using the morphological mutant "amycelial"--a conditional, aconidial strain of N. crassa--have revealed certain consistent functional and biochemical differences from wild type strains showing normal morphology and conidia formation. Thus it was found that the mutant strain showed an abnormal utilization of protein reserves at a time when there is extensive degradation during conidiogenesis in wild type. In addition, the mutant exhibited abnormally low oxygen consumption and free amino acid pools depressed nearly 3/4 with respect to wild type. All of these findings are consistent with earlier work linking conidiogenesis to aerobic oxidative processes and suggest that catabolic reactions particularly regarding protein breakdown may be important to conidiogenesis from the standpoint of the synthesis of new conidial proteins and for the supply of endogenous energy reserves during the process. The aconidial character of "amycelial" could be partially alleviated on solid acetate medium supplemented with amino acids, especially tryptophan or histidine. Conidiation was also induced by cyclic-AMP, even on sucrose medium. A polymer strongly antigenic in rabbits was found to be released into growth medium by the mutant but not by wild type cultures, providing a possible clue to the immediate cause of the abnormal morphology seen in "amycelial". This substance appears to be a glycopeptide containing a few hexoses and amino acids associated with polyphosphate.

Amino Acids↗