Bacteriophage and bacteriophage-like structures carried by Bacillus medusa and their effect on sporulation

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Abstract
B. medusa carried 3 phages or phagelike structures named .vphi.med-1, .vphi.med-2 and .vphi.med-3. .vphi.Med-1 is a minute, 25-nm-diameter particle without a tail. It was extracted from the sporulation lysate of a .vphi.med-2-minus strain of B. medusa and purified by differential centrifugation. The nucleic acid from this structure was orcinol positive, alkali sensitive, RNase sensitive and DNase resistant. An RNase-resistant core of nucleic acid was not found, indicating that it was single-stranded RNA. A host strain was not yet found for .vphi.med-1. Phage .vphi.med-3 was induced with mitomycin C or UV light and consisted of empty heads of 57 nm in diameter, whereas .vphi.med-2 induced with mitomycin was a phage of 60-nm head diameter and 220-nm tail length. The sporulation sequence proceeded faster in those mutants lacking .vphi.med-2, and when the phage was reintroduced to B. medusa the extended wild-type sporulation sequence was observed. B. thuringiensis var. schwetzova was sensitive to .vphi.med-2 and yielded small turbid plaques. B. medusa produced small numbers of .vphi.med-2 during growth. The other phage may be produced at the same time but were not detected. .vphi.Med-1 was found in sporulating cells by EM techniques. Its release from these was demonstrated by EM techniques and a radioactive assay. It appears to participate in the formation of a surface layer on the parasporal inclusion of B. medusa.