FIG 2.

Growth of A. niger on various guanidinium compounds. (Top) Spores (equal numbers) of A. niger (the WT, D-42, and ΔXCA-29 strains) were spot inoculated on media containing different nitrogen sources (20 mM with respect to total N), namely, l-arginine (Arg), agmatine (Agm), 4-guanidinobutyrate (GB), 3-guanidinopropionate (GP), d-arginine (D-Arg), l-homoarginine (H-Arg), and guanidinoacetate (GAA). (Bottom) The corresponding growth patterns on urea and the respective amino products (namely, l-ornithine [Orn], putrescine [Put], and 4-aminobutyric acid [GABA]) of ureohydrolase action. The results for controls with ammonium nitrate (NH₄NO₃) and no nitrogen source (−N) are also shown. Growth was recorded at two time points.