A bacteriocin produced spontaneously by a nontoxigenic strain of Clostridium botulinum, type E, PM-15, has been isolated and designated boticin P. It was purified by ammonium sulfate precipitation, gel filtration on Sephadex G-100, sucrose density gradient centrifugation, and cesium chloride equilibrium density gradient centrifugation. Boticin P is composed mainly of proteins (98.8%) with a trace amount of carbohydrates (0.4%), and has an apparent molecular weight in excess of 4 × 106 daltons as estimated by gel filtration on Sepharose 2B. Electron microscopic examination of boticin P reveals a phage tail-like structure of 100 nm in length.Boticin P exerted a static effect on vegetative growth and spore outgrowth but not on the initial events of germination. The boticin was active on 10/12 toxigenic and 3/6 nontoxigenic type E and 2/2 nonproteolytic type B strains of C. botulinum. The activity spectrum on 27 strains supports the proposal that type E and the nonproteolytic type B strains belong to the same taxosubspecies.

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