Some Studies on the Competitive Colonisation of Cellulosic Substrates by Microorganisms

Abstract

In an investigation of aspects of the competitive colonisation of straw by microorganisms, fungi were first isolated from samples of straw to determine the predominant species present. Straw treated with ammonia solutions was also isolated from; under these conditions, Coprinus cinereus became the dominant fungus. After screening the more commonly occurring cellulolytic fungi for high linear growth rate and cellulolytic ability, eight fungi were selected for further studies. An assessment of the optimum pHs and temperatures for linear growth showed how particular fungi may be encouraged to dominate the colonisation of straw by control of one or both of these parameters. The eight fungi varied considerably in their ability to break down straw in pure culture, C. cinereus and Fusarium culmorum being rather better than the others, and tests indicated that C. cinereus and two other fungi may be able to cause some breakdown of lignin. Most of the more commonly isolated fungi were found to be capable of inhibiting the growth of others in interaction studies. This ability varied widely, Trichoderma spp. possessing by far the greatest capacity, followed by C. cinereus and then Chaetomium globosum. C. cinereus was generally more successful at higher pHs. Tests on C. cinereus indicated that no powerful stable volatile or non-volatile toxins effective against the assay fungi used are produced. Several fungi showed an aggressive ability towards C. cinereus in microscopic studies of hyphal interaction. C. cinereus appeared to possess little or no aggressive ability. The study suggests that domination of straw by C. cinereus is favoured by alkaline pHs and high temperatures, and points to the way these and other factors may affect competition by other fungi.