Exogenous carbon and nitrogen requirements for conidial germination by <i>Aspergillus flavus</i>

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 NH 4 Cl supported higher germination than several other single amino acids or single sugars plus NH 4 Cl tested. When exogenous carbon was supplied as glucose, total and percentage germination of washed conidia were influenced more by exogenous nitrogen, supplied as NH 4 Cl, as the conidial density increased and as the glucose and NH 4 Cl 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 CO 2 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.