Multiple proteolytic enzyme production in keratinophilic fungi (preliminary investigations) : a thesis presented in fulfilment of the requirement for the degree of Master of Science in Microbiology, Massey University

Abstract

Superficial fungal infections can be acquired from a number of sources, e.g. animals, humans or from the soil. Many of the fungal species commonly associated with human disease arise from infection by species known commonly as dermatophytes, although infection from other non-dermatophytic keratinophilic fungi is becoming more common. Other species not commonly regarded as pathogenic have on occasion been found in human infection. Many of these opportunistic species are commonly found in soils. Isolation procedures employed in these studies were the hairbrush technique for small animals and the keratin-baiting technique for soil with samples being cultured on SDA containing antibiotics. Soil samples yielded 3 keratinophilic genera found in human infection (Microsporum spp.. Trichophyton spp. Aphanoascus sp.) while fungi isolated from animals yielded 3 fungal species. Microsporum canis. Microsporum cookei and Scopulariopsis brevicaulis. In these studies, various culture parameters e.g. pH, spore numbers and various hydrolysis techniques were examined in order to asses the production of proteolytic enzymes in vitro. Also in the course of these studies, the use of lactrimel medium as a suitable recovery agent for strains presenting atypical colony morphology and reduced proteolytic enzyme production was trialed with excellent results. The gelatin SDS-PAGE technique, mode of culture (shake and stationary) and the effect of substrate were analysed to compare the effects that these have on a range of keratinophilic fungi. Both pathogens and saprophytes were examined in an attempt to detect similarities in enzyme production which could be associated with the ability of various species to invade skin in vivo. A large body of data has been gathered demonstrating that the proteolytic enzymes produced by most keratinophilic fungi encompass a wide range of MW sizes and are not entirely predictable. This strongly suggests that when these fungi come into contact with a particular substrate, the ability of the strain to adapt may depend on the strains ability to produce a proteolytic enzyme capable of breaking down the substrates in the external environment providing nutrients for the growing fungi.