The Chaetomium species belong to the class Ascomycetes. The imperfect form (axesual) belongs to the class Deuteromycetes (Botryotrichum). This endophyte fungus contains about one hundred cellulolytic species.
The colonies are downy, rapid-growing, and gray to olive-green. The ostiolate perithecia are large, dark brown to black, and are lined with simple or branched hairs which are straight, wavy or more or less spiral. These perithecia contain cylindrical or claviform asci, emitting 4 to 8 unicellular, black, smooth ascospores that are globular, ovoid or elliptical. The optimum growth temperature for Chaetomium is 50 °C and the spores can withstand a maximum temperature of 60 °C.
The Chaetomium species are cosmopolitan, ubiquitous, and very common in the environment. They can be plant pathogens and are involved in various human infections caused by the production of mycotoxins (chaetomin, chaetoglobosin, sterigmatocystin). They are of interest for the industrial production of cellulase and protein.