Onygena species. Non-pathogenic species of Onygenales, are specialized in breaking down the keratin found in feather, hooves, and horn. The keratin is composed of proteins, bound in a non-bio-accessible form. Among the large number of different proteases produced by O. corvina, we discovered that just three enzymes, belonging to two types of protease families, are sufficient to breakdown both feather and pig bristles. The picture shows O.equina growing on horn, but not on the skull (Northern Ireland, 2012). Photo: Jens H. Petersen.