FIG 7.

Phenotypic analysis of A. niger Δgbu-90 (GBase disruptant) and its parent, A. niger MA169.4 (ΔkusA). Spores (equal numbers) were spotted on minimal media containing different nitrogen sources (15 mM with respect to total N), namely, agmatine (Agm), 4-guanidinobutyrate (GB), 4-aminobutyric acid (GABA), and urea. Controls for growth on ammonium nitrate (NH₄NO₃) and no nitrogen source (−N) are also shown. Growth was recorded at 60 h. Medium without uracil (10 mM) served to show that A. niger Δgbu-90 is a uracil prototroph and also for utilization of uracil as a nitrogen source.