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Curr Microbiol (2008) 57:153157
DOI 10.1007/s00284-008-9168-y
Ferrous, But Not Ferric, Iron Maintains Homeostasis in Histoplasma capsulatum Triacylglycerides
Robert Zarnowski Agnieszka Dobrzyn James M. Ntambi Jon P. Woods
Received: 16 February 2008 / Accepted: 18 March 2008 / Published online: 28 May 2008 Springer Science+Business Media, LLC 2008
Abstract Iron is an indispensable micronutrient for virtually all microorganisms, where it acts as a cofactor of many enzymes involved in regulation of multiple cellular and physiological functions. This metal is also considered an important determinant contributing to the pathogenesis of fungal infectious diseases, and therefore the identication of iron-regulated metabolic processes occurring within the invading fungal cell can help the development of new anti-fungal therapeutic strategies. In this study, we examined relationships between iron availability and neutral storage lipids in Histoplasma capsulatum, a dimorphic fungus responsible for the most common respiratory and systemic mycosis in humans. Yeast cells were grown in a dened minimal medium supplemented with or without iron. Lipids were extracted from cells at the log and late stationary growth phases, then separated by thin-layer chromatography, and fatty acids were analyzed by gas chromatography. A culture age-related decrease in the unsaturated fatty acid content was observed in all four neutral lipid classes
examined. Iron-related alterations could be seen in relation to triacylglycerol and free fatty acid pools, whereas no iron-dependent effects were detected in diacylglycerol and steryl ester fractions. Regarding triacylglycerols, the presence of iron positively affected the content of unsaturated fatty acids, and this stabilizing action of iron was notably increased when ferrous ions were added. Subsequent iron uptake studies showed a denite preference of H. capsulatum to acquire iron in its reduced, more soluble, ferrous form, and therefore, the availability of iron may be the underlying reason for the observed iron-maintained homeostasis in H. capsulatum triacylglycerols.
Introduction
Iron is essential for virtually all living organisms, where it acts as a cofactor of many enzymes and is involved in multiple vital cellular and physiological functions. This metal exists in nature predominantly in the insoluble oxidized Fe3+ form and its accessibility to living organisms is, in general, drastically limited. In Saccharomyces cerevisiae, iron scarcity results in a substantial transcriptional remodeling of expression patterns of multiple genes leading to tremendous alterations in numerous metabolic traits, including...