Effect of Combined Bacterial and Urea Treatment on Biodegradation of Wood by Basidiomycete Fungi

A laboratory investigation of the effect of two ureolytic bacteria (Proteus sp. and Bacillus sp.) on growth of woodrot fungi (Gloeophyllum sepiarium, Gloeophyllum sp., Pleurotus sp. and Trametes sp.) in media and wood containing urea, was carried out. Biomass of the wood-rot ftingi was markedly reduced in potato dextrose/peptone/ urea (PDPU) broth to which ureolytic bacteria was introduced after 4 days growth of the fungi. Interaction studies on non-urea containing agar plates did not indicate any antagonism between bacteria and wood-rot fungi while sterile filtrates from 24 h PDPU cultures of ureolytic bacteria indicated that presence of ammonia prevented or markedly reduced growth of the fungi. Bacterial ureolytic activity produced volatiles which reduced wood-rot fungal growth. Biodegradation was markedly reduced in wood treated with urea and ureolytic bacteria before exposure to wood-rot fungi. Similar treatment of wood previously inoculated with the fungi significantly retarded on-going decay. Wood-rot fungi isolated from treated wood showed reduced growth. Inhibition of wood-rot fungal activity is attributed to production of ammonia by the bacteria and the stress imposed by the resultant hostile alkaline pH.