Hydrolytic enzyme activity of Paenibacillus sp strain B2 and effects of the antagonistic bacterium on cell integrity of two soil-borne pathogenic fungi

Paenibacillus sp. strain B2, isolated from the mycorrhizosphere of Sorghum bicolor and having an antagonistic activity towards soil-borne fungal patho gens, possessed extracellular cellulolytic, proteolytic, chitinolytic and p ectinolytic enzyme activities. The eventual role of these lytic enzymes in cellular interactions between Paenibacillus sp. strain B2 and Phytophthora parasitica and Fusarium oxysporum was investigated by electron microscopy a nd molecular cytology. Electron microscopic observations showed that the pr esence of Paenibacillus sp. strain B2 resulted in disorganisation of cell w alls and/or cell contents of P. parasitica and F. oxysporum. However, when P. parasitica was treated with commercial purified cellulase, protease, chi tinase and pectinase, only protease had an inhibitory effect on mycelial gr owth. It is proposed that the inhibitory effect of Paenibacillus sp. strain B2 on the growth of soil-borne fungal pathogens is probably derived from m ore than one mechanism. (C) 2000 Elsevier Science B.V. All rights reserved.