ANTIBIOTIC PRODUCTION BY ERWINIA-HERBICOLA EH1087 - ITS ROLE IN INHIBITION OF ERWINIA-AMYLOVORA AND PARTIAL CHARACTERIZATION OF ANTIBIOTIC BIOSYNTHESIS GENES

Mutants of Erwinia herbicola Eh1087 (Ant(-)), which did not produce an tibiotic activity against Erwinia amylovora, the fire blight pathogen, were selected after TnphoA mutagenesis, In immature pear fruit Ant(-) mutants grew at the same rate as wild-type strain Eh1087 but did not suppress development of the disease caused by E. amylovora, These resu lts indicated that antibiosis plays an important role in the suppressi on of disease by strain Eh1087, All of the Ant-mutations obtained were located in a 2,2-kb region on a 200-kb indigenous plasmid, Sequence a nalysis of the mutated DNA region resulted in identification of six op en reading frames, designated ORF1 through ORF6, four of which were es sential to antibiotic expression. One gene was identified as a gene wh ich encodes a translocase protein which is probably involved in antibi otic secretion. A sodium dodecyl sulfate-polyacrylamide gel electropho resis analysis of plasmid proteins produced in Escherichia coli minice lls confirmed the presence of proteins whose sizes corresponded to the sizes of the predicted open reading frame products.