Studies on the Colonization and Degradation of Human Hair by Streptomyces fradiae

Abstract

Experiments in which Streptomyces fradiae was grown on ether-extracted, ethylene oxide-sterilised human hair as sole carbon and nitrogen source have demonstrated the ability of the organism to bring about the complete structural degradation of the substrate. Electron micrographs reveal the colonisation and subsequent deterioration of the hair fibres. Photographic evidence shows that the microbial attack is uniform along the hair fibre and not localised to specific areas of colonisation. There is little evidence to suggest that degradation is initiated by mechanical disruption of the hair by penetrating hyphae. Time course studies clearly show the systematic removal of distinct histological regions of the hair fibres. Initially the epicuticle is clearly visible. This becomes obscured as colonisation proceeds. Removal of microbial growth by gentle washing reveals a layer that lies between the epicuticle and the cortex, possibly the exocuticle, endocuticle or outer regions of the cortical matrix. Later micrographs reveal the cortex below. Finally the disintegration of the cortex into individual cells is observed.

Culture supernatants have been found to have an optimum keratinolytic activity at pH 9·0. At this pH the specific activity of culture supernatants is approximately ten times greater than that of commercially available keratinolytic enzymes.