Studies on the molecular ecology of Blastomyces dermatitidis

The microecology of Blastomyces dermatitidis, the dimorphic etiologic agent of the potentially fatal systemic fungal infection, blastomycosis, is not well defined. Blastomyces dermatitidis may occur periodically at natural si tes, perhaps aided by rotting organic material, animal droppings and physic al changes. Semi-quantitative growth studies of B. dermatitidis on 2% agar plates determined the ability to utilize or tolerate a variety of substrate s including simple and complex molecules as carbon source, and organic and inorganic nitrogen sources. Allantoin, creatinine, quanidoacetic acid, guan idine and cysteine may be used as sole nitrogen source. Allantoin in combin ation with dextrose, glycerol, lichenen, celloboise and other wood by-produ cts support growth of B. dermatitidis at room temperature. The nutritional conversion of the fungus to the yeast form at room temperature, well demons trated on allantoin/glycerol/yeast extract media, appears to be affected by certain inorganic compounds. The organism tolerates low to moderate levels of alpha-pinene, tannic acid, shikimic acid, veratryl alcohol, vanillic ac id, and polyethyleneglycol-200. There are significant differences among iso lates regarding growth on various substances at 20 degrees and 37 degrees c entigrade. It appears that a variety of wood by-products and animal waste s ubstrates, in combination, support the growth of B. dermatitidis. Their rol e in the ecological niche of B. dermatitidis, and the importance of nutriti onal dimorphism in the natural environment warrants further investigation.