Related Experiment Videos
Hydroxamate siderophores of Histoplasma capsulatum
D H Howard1, R Rafie, A Tiwari
1Department of Microbiology, Neuropsychiatric Institute, UCLA School of Medicine, Los Angeles, California, USA. dhoward@ucla.edu
Abstract:
The zoopathogenic fungus Histoplasma capsulatum, like other eukaryotic aerobic microorganisms, requires iron for growth. Under conditions of low iron availability, the fungus secretes hydroxamates that function as siderophores (iron chelators). The experiments to be reported were designed to gather further information on the hydroxamate siderophores of H. capsulatum. The fungus 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 microM iron. The secretion was suppressed by 10 microM iron. The hydroxamates were purified by reverse-phase and size-exclusion chromatography. On the basis of ions observed during electrospray 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 generated. This reagent cross-reacted with coprogen B and fusarinine. Thus, the antibody detects hydroxamates in all three families of siderophores excreted by H. capsulatum.
Insights
Histoplasma capsulatum secretes hydroxamate siderophores for iron acquisition. Researchers identified five siderophores and developed an antibody that detects multiple types, aiding fungal iron metabolism studies.
Area of Science:
- Mycology
- Biochemistry
- Microbiology
Background:
- The zoopathogenic fungus Histoplasma capsulatum requires iron for growth, similar to other aerobic microorganisms.
- Under iron-limiting conditions, H. capsulatum secretes hydroxamates, which act as siderophores (iron chelators).
Purpose of the Study:
- To investigate the hydroxamate siderophores produced by H. capsulatum.
- To identify and characterize the specific siderophores secreted by the fungus.
Main Methods:
- Fungal growth in a deferrated synthetic medium using Chelex 100.
- Detection of siderophores under varying iron concentrations (0.3–1.0 µM iron, suppressed by 10 µM iron).
- Purification via reverse-phase and size-exclusion chromatography, followed by electrospray mass spectrometry.
Main Results:
- Five hydroxamate siderophores were tentatively identified: dimerum acid, acetyl dimerum acid, coprogen B, methyl coprogen B, and fusarinine.
- A polyclonal antibody against dimerum acid was generated.
- The antibody demonstrated cross-reactivity with coprogen B and fusarinine.
Conclusions:
- The study identified key hydroxamate siderophores involved in iron uptake by H. capsulatum.
- The developed antibody is a valuable tool for detecting multiple families of siderophores secreted by this fungus.
- These findings contribute to understanding iron metabolism in pathogenic fungi.