The possible role of uric acid in the ecology of Histoplasma capsulatum

Abstract

The results of this study indicate that Histoplasma capsulatum in its saprophytic form is able to utilize the major nitrogenous constituent of avian manure as a nitrogen source. In addition, the enzymes responsible for the pathway of uric acid degradation to inorganic nitrogen have been demonstrated in cell-free systems. These enzymes include uricase, allantoinase, allantoicase, and urease. The uricase of Histoplasma appears to be a cell wall or cell membrane-associated enzyme, while the other enzymes were located in the soluble portion of cell-free extracts. Cell-free extracts of Cryptococcus neoformans are actively uricolytic. It is suggested that this ability of H. capsulatum hyphae to utilize uric acid and related compounds as growth substrates may in part explain the indisputable ecologic association of this pathogenic fungus with avian and possibly chiropteran-associated soils and habitats in those areas endemic for histoplasmosis. © 1968 Dr. W. Junk N.V.