Antibiotics in microbial ecology

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Abstract
Nine strains of the terrestrial bacterial genusXenorhabdus, all isolated as symbionts of nematodes, were examined for their abilities to produce substances with antibiotic activites when grown in pure culture. All nine produced measurable antibiotic activities against one or more of the test strains utilized. The inhibition patterns indicated that different compounds were being produced by the various bacteria. Two of the species that showed particularly strong inhibition patterns were studied in detail. The inhibitory compounds were purified and identified. Strain R produced a mixture of active substances, the major components of which were hydroxyl- and acetoxyl-bearing indole derivatives, presumably produced via tryptophan. Strain Hb, on the other hand, produced only two antibiotics, 4-ethyl- and 4-isopropyl-3,5-dihydroxy-trans-stilbenes, which are presumed to arise via polyketide pathways.