Hydroxamate siderophores of Histoplasma capsulatum

The zoopathogenic fungus Histoplasma capsulatum, like other eukaryotic aero bic microorganisms, requires iron for growth. Under conditions of low iron availability, the fungus secretes hydroxamates that function as siderophore s (iron chelators). The experiments to be reported were designed to gather further information an the hydroxamate siderophores of H. capsulatum. The f ungus was grown in a synthetic medium deferrated with the cationic exchange resin Chelex 100, Siderophores were detected after 4 days of incubation at 37 degrees C in media containing 0.3 to 1.0 mu M iron. The secretion was s uppressed bg 10 mu M iron. The hydroxamates were purified by reverse-phase and size-exclusion chromatography. On the basis of ions observed during ele ctrospray mass spectroscopy, five hydroxamate siderophores were tentatively identified: dimerum acid, acetyl dimerum acid, coprogen B, methyl coprogen B, and fusarinine (monomeric). A polyclonal antibody to dimerum acid was g enerated. This reagent cross-reacted with coprogen B and fusarinine, Thus, the antibody detects hydroxamates in all three families of siderophores exc reted by H. capsulatum.