FIG. 4.

Mycelial growth, siderophore production, and dimerum acid levels in G20-4VIB and Psy1 disruptants. Spores of G20-4VIB (wild type) (circles) or Psy1 disruptants T31 (triangles) and T155 (squares) were inoculated into a base medium used to limit trace iron (<0.1 μM Fe), and the resulting cultures were divided into equivalent 10-ml cultures. Supplemental iron was added to one-half of the flasks to create high-iron conditions (100 μM Fe) (open symbols), while the other cultures were not supplemented in order to create low-iron conditions (solid symbols). Triplicate cultures were harvested by filtration at different times after inoculation for the wild-type and T31 strains. Duplicate cultures were harvested for strain T155. The dry weight of the mycelium in each 10-ml culture (A) and the total hydroxamate siderophore yield for each culture filtrate (B) are shown. To determine the total amount of hydroxamate utilized, we performed an Fe(ClO₄)₃ assay with samples of culture filtrate that were not purified. The error bars indicate standard errors of the mean. (C) Dimerum acid levels in the culture filtrates analyzed by methanol extraction, purification on XAD-2 resin, and TLC. The only band was the Fe(ClO₄)₃-stained band on TLC chromatograms, and this band comigrated with a dimerum acid standard. Lane C contained a control extraction of uninoculated culture medium.