CLONING AND CHARACTERIZATION OF AEROBACTIN BIOSYNTHESIS GENES OF THE BIOLOGICAL-CONTROL AGENT ENTEROBACTER-CLOACAE

Five strains of Enterobacter cloacae that are biological control agent s of Pythium damping-off diseases produced the hydroxamate siderophore aerobactin under iron-limiting conditions. Genes determining aerobact in biosynthesis of the biocontrol strain E. cloacae EcCT-501 were loca lized to a 12.3-kb region, which conferred aerobactin production to Es cherichia coli DH5alpha The aerobactin biosynthesis genes of E. cloaca e hybridized to those of the pColV-K30 plasmid of E. coli, but restric tion patterns of the aerobactin regions of pColV-K30 and E. cloacae di ffered. A derivative strain with a deletion in the aerobactin biosynth esis locus was as effective as strain EcCT-501 in biological control o f Pythium damping-off of cucumber. Thus, aerobactin production did not contribute significantly to the biological control activity of EcCT-5 01 under the conditions of this study.