Chrysosporium keratinophilum
Chrysosporium keratinophilum is a mold that is closely related to the dermatophytic fungi (Family Arthrodermataceae) and is mainly found in soil and the coats of wild animals to break down keratin. Chrysosporium keratinophilum is one of the more commonly occurring species of the genus Chrysosporium in nature. It is easily detected due to its characteristic "light-bulb" shape and flat base. Chrysosporium keratinophilum is most commonly found in keratin-rich, dead materials such as feathers, skin scales, hair, and hooves. Although not identified as pathogenic, it is a regular contaminant of cutaneous specimens which leads to the common misinterpretation that this fungus is pathogenic. Description Chrysosporium keratinophilum colonies grow rapidly at 25 °C approximately 60–100 mm in 21 days. Colonies can be flat or folded, dry, powdery, or velvety with a white- or cream-coloured center The colony surface is dotted with droplets of clear or brown exuded liquid. The hyphae are septate and the conidia are hyaline, broad-based and one-celled. The conidia are large, smooth to slightly rough-walled, sometimes slightly curved and occasionally septate. The conidia are broadly "light-bulb" shaped with an abruptly flattened smooth base. Colonies grow to about 30 mm in diameter in one week and are flat with a powdery to suede-like texture. The colony reverse is also cream-coloured. Chrysosporium keratinophilum produces abundant aleurioconidia that resemble the microconidia of dermatophytes; however, the conidia of C. keratinophilum are considerably larger. Chrysosporium keratinophilum has been associated with two closely related sexual states: Aphanoascus keratinophilus and Aphanoascus fulvescens. Habitat and distribution Chrysosporium keratinophilum is often referred to as a keratinophilic fungus in reference to its affinity for growth on keratin-rich non-living materials such as skin scales and hairs separated from the host. Chrysosporium keratinophilum produces a keratin-degrading enzyme that functions at 90 °C. Its process of digestion occurs in two stages, requiring keratin to be chemically altered to a structureless form before it is digested. The method of hair digestion is carried out with perforating bodies. Chrysosporium spp. are asexual states of fungi in the genera Aphanoascus, Nannizziopsis, and Uncinocarpus. The fungus commonly grows on feathers, hooves, hair and other dead matter. It is rarely found on human skin and more commonly found in soil in temperate areas, plant material, dung and on birds. A study on keratinophylic fungi in the water sediments of India, by Katiyar and Kushwaha, found C. keratinophilum in sediments of catch basins and sewage sludge in India and Poland. Chrysosporium keratinophilum is associated to mud sludge structure, high humidity, volatile solids, low carbon nitrogen ratios and tolerance to heavy metals. Together, these give C. keratinophilum a high long-term survival probability in superficial water which may present an exposure risk, especially to people in India who bathe in these waters. Apart from inhabiting water sediments, a study in Egypt identified and isolated the teleomorph of C. keratinophilium, Aphanoascus fulvescens, in half of samples gathered from floor dusts in university student housing, demonstrating its regularity in indoor environments. Similarly, Bahkali and Parvez found C. keratinophilum to be widespread mold