CHARACTERIZATION OF GENES INVOLVED IN BIOSYNTHESIS OF A NOVEL ANTIBIOTIC FROM BURKHOLDERIA-CEPACIA BC11 AND THEIR ROLE IN BIOLOGICAL-CONTROL OF RHIZOCTONIA-SOLANI

Genetic manipulation of fluorescent pseudomonads has provided major in sight into their production of antifungal molecules and their role in biological control of plant disease. Burkholderia cepacia also produce s antifungal activities, but its biological control activity is much l ess well characterized, in part due to difficulties in applying geneti c tools. Here we report genetic and biochemical characterization of a soil isolate of B. cepacia relating to its production of an unusual an tibiotic that is very active against a variety of soil fungi. Purifica tion and preliminary structural analyses suggest that this antibiotic (called AFC-BC11) is a novel lipopeptide associated largely,vith the c ell membrane. Analysis of conditions for optimal production of AFC-BC1 1 indicated stringent environmental regulation of its synthesis. Furth ermore, we show that production of AFC-BC11 is largely responsible for the ability of B. cepacia BC11 to effectively Control the damping-off of cotton caused by the fungal pathogen Rhizactonia solani in a gnoto biotic system. Using Tn5 mutagenesis, we identified, cloned, and chara cterized a region of the genome of strain BC11 that is required for pr oduction of this antifungal metabolite. DNA sequence analysis suggeste d that this region encodes proteins directly involved in the productio n of a nonribosomally synthesized lipopeptide.