ANTIFUNGAL, SYNERGISTIC INTERACTION BETWEEN CHITINOLYTIC ENZYMES FROMTRICHODERMA-HARZIANUM AND ENTEROBACTER-CLOACAE

Biocontrol strains from the genera Enterobacter and Pseudomonas and tw o chitinolytic enzymes from Trichoderma harzianum isolate P1 were comb ined and tested for antifungal activity in bioassays. Inhibitory effec ts on spore germination and germ tube elongation of Botrytis cinerea, Fusarium solani, and Uncinula necator were synergistically increased b y mixing fungal enzymes and cells of Enterobacter cloacae but not of P seudomonas spp. Culture filtrate of E. cloacae contained antifungal co mpounds and produced moderate levels of inhibition, either in plate as says or in bioassays conducted in potato-dextrose broth. However, the combination of bacterial culture filtrate with fungal chitinolytic enz ymes generated only an additive response, indicating that the presence of bacterial cells was required for a synergistic effect. Chitinolyti c enzyme activity in the presence of chitinous substrates enhanced the growth of E. cloacae and readily restored the ability of bacterial ce lls to bind to hyphae of the pathogens despite high concentrations of D-glucose or sucrose in the medium. The results of this study suggest that transgenic bacteria, capable of binding to fungal cell walls and expressing fungal genes encoding cell wall-degrading enzymes, may be p owerful biocontrol agents.