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Disease Control and Pest Management

Multiple Antibiotic Production by Erwinia herbicola. Carol A. Ishimaru, Graduate student, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, Present address: Department of Plant Pathology, University of Nebraska, Lincoln 68583; Edward J. Klos(2), and Robert R. Brubaker(3). (2)Professor, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; (3)Professor, Department of Microbiology and Public Health, Michigan State University, East Lansing 48824. Phytopathology 78:746-750. Accepted for publication 11 December 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-746.

Cells of Erwinia herbicola strain C9-1 produced at least two antibiotics, termed herbicolin O and herbicolin I, when grown at 30 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 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.