Exogenous carbon and nitrogen requirements for conidial germination by Aspergillus flavus.

Abstract

In a phosphate-buffered (pH 5.7) inorganic salts solution (B), nearly full dependence on exogenous carbon was found for germination of washed, Tween 20-treated conidia of Aspergillus flavus over a range of conidial densities. No exogenous carbon-independent germination was observed for settling tower-deposited dry conidia. At equivalent carbon, an amino acid mixture supported highest germination of washed conidia; proline, alanine, or glucose plus NH4Cl supported higher germination than several other single amino acids or single sugars plus NH4Cl tested. When exogenous carbon was supplied as glucose, total and percentage germination of washed conidia were influenced more by exogenous nitrogen, supplied as NH4Cl, as the conidial density increased and as the glucose and NH4Cl concentrations increased. At equivalent nitrogen, proline alone, or certain amino acid mixtures supported highest germination of several nitrogen sources in B solution plus glucose. Germination decreased as the conidial density decreased when exogenous carbon and nitrogen were supplied at each density at constant amounts per conidium. Removal of CO2 from the germination medium inhibited germination. Tween 20 and Tergitol NPX stimulated germination of settling tower-deposited conidia. "Amino acid carry-over" for conidial germination was not demonstrated. The possible relation of these findings to the ecology of conidial germination in soil is discussed.