Keratinophilic fungi: Their role in nature and degradation of keratinic substrates

Keratinophilic fungi are natural colonizers of keratinic substrates. Some are keratinolytic and play an important ecological role in decomposing α-keratins, the insoluble fibrous proteins. Because of the tight packing of their polypeptide chains in α-helix structures and their linkage by disulphide bridges, they are poorly biodegradable. Two main forms of attack have been identified: surface erosion and radial penetration. In surface erosion, the sequence of degradation proceeds as the level of keratinisation (the cystine crosslinks) of the components of the keratinic matrix increases. In radial penetration, on the other hand, specialized hyphae can penetrate like a drill throught the matrix, irrespective of the degree of keratinisation. This may illustrate how the growth can change direction and how secretory activity may concentrate at the tips of the penetrating hyphae.