Production of elastase by pathogenic and non-pathogenic fungi.

Abstract

Many yeasts, dermatophytes as well as moulds liberate hydrolytic enzymes into the growth medium. The enzymes may serve the fungus by different ways, e. g., they cause chemical and physical changes in the immediate surrounding of the fungus thus enhancing the living possibilities. The production of enzymes capable of digesting mammalian proteins would aid pathogenic fungi to penetrate the human epidermis and to spread in the dermis. Many of the dermatophytes are, in fact, capable of digesting keratin by the aid of keratinase, collagen by the aid of collagenase (RIPPON and LORINCZ, 1964) and even elastin by the aid of elastase (RIPPON and VARADI, 1968). Elastase and collagenase could serve the organism also by breaking the intercellular connection of the epidermal cells or by dissolving the basal membrane (KOTRAJARAS, 1965). The production of elastase, one of the most specific proteases by fungi has been the subject of only one report in which relatively few species were tested (RIPPON and VARADI, 1968). Further studies on the elastase producing ability of the pathogenic as well as non-pathogenic fungi might clarify the role of this enzyme in the pathogenicity of the fungi. They could also disclose whether tests on the elastase production could be of value in the routinly identification of fungi. Material and methods The production of elastase by growing colonies of yeasts, dermatophytes and moulds was tested by using two kinds of test agar plates. The basic growth medium was the same in both types of plates containing glucose 10.0 g, pepton aus casein (Merdc) 5.0 g, glycerol 5.0 g, sodium chloride 5.0 g, Standard I1 Nahrbouillon Merdc 15.0 g, agar 30.0 g, yeast extract 3.0 g and aqua destillata 1000 ml. One gram of elasdn powder (Sigma Chem. Comp.) was added to 100 ml sterilized agar which was poured on test plates thus following essentially the method of R~PPON and VARADI (1968). In these plates the grains of elastin appear gray against the yellowish badrground. Elastase activity was manifested as dissolution of the grains and thus as the appearance of a clear ring around the colony. In the second type of growth plates the elastin was replaced by elastin which was coupled with Remazolbrilliant Blue B according to RINDERKNECHT (1970). In these plates (incubated at 23' C) the grains are dark blue and after dissolution of the grains a clear ring is seen. The zones of cleraing around the fungi were recorded after 4, 7, and 14 days respectively. The species of fungi tested were from the collection of our laboratory (most of them are originally from Centraalbureau voor Schimmelcultures, Holland).