Multiple Antibiotic Production byErwinia herbicola

Abstract

Cells of Erwinia herbicola strain C9-1 produced at least two antibiotics, termed herbicolin O and herbicolin I, when grown at 30.degree.C in a chemically defined medium containing D-gluconate and L-asparagine as sources of energy. Herbicolin O inhibited growth of a wide variety of a limited number of tested procaryotes, including Erwinia amylovora strain 110, other erwiniae, Enterobacter aerogenes, Escherichia coli, Serratia marcescens, Proteus species, yersiniae, shigellae, salmonellae, and Bacillus cereus. In contrast, the antibacterial spectrum of herbicolin I was limited to E. amylovora, B. cereus, and Staphylococcus aureus. Mutants of E. amylovora were selected that exhibited resistance to herbicolin O but not herbicolin I and vice versa. In addition, antibacterial activity of herbicolin O, but not that of herbicolin I, was inhibited by by L-histidine. An evidently related herbicolin was produced by E. herbicola strain 112Y. Treatment of immature pear fruit slices with whole cells of E. herbicola strain C9-1 or with partially purified herbicolins promoted significant reduction in severity of disease caused by E. amylovora. These findings are consistent with the suggestion that herbicolins serve to control fire blight naturally, providing a basis for further study of herbicolins'' structure and mode of action.