Septate hyphae, perithecia, asci and ascospores are visualized. Perithecia are large, dark brown to black in color, fragile, globose to flask shaped and have filamentous, hair-like, brown to black appendages (setae) on their surface. Perithecia have ostioles (small rounded openings) and contain asci and ascospores inside. Asci are clavate to cylindrical in shape and rapidly dissolve to release their ascospores (4 to 8 in number). Ascospores are one-celled, olive brown in color, and lemon shaped. Chaetomium colonies are rapidly growing, cottony and white in color initially. Mature colonies become grey to olive in color. From the reverse, the color is tan to red or brown to black
Chaetomium are a common fungal species with a ubiquitous distribution with over 80 species currently known. Chaetomium colonies are rapidly growing, cottony and white in color initially. Mature colonies become grey to olive in color. From the reverse, the color is tan to red or brown to black. Fruiting structures of this mold look like olive-green cockleburs – 1/16 inch in diameter – that develop on compost. Although its heat tolerant spores survive 140 F for 6 hours, the mold appears only in compost improperly managed during Phase II, especially where Phase II ventilation is inadequate. Lack of oxygen when compost temperatures are greater than 142 F permits formation of compounds produced in anaerobic conditions. These compounds are toxic to spawn growth but are utilized by the olive green mold. It is highly cellulolytic.
This fungus is reported to be allergenic and a toxin. It is an ascomycete and in most species the spores are lemon-shaped.
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