ISOLATION AND CHARACTERIZATION OF COVALENTLY CLOSED CIRCULAR DNA ASSOCIATED WITH CHROMOSOMAL AND MEMBRANE FRACTION FROM STREPTOMYCES AMBOFACIENS

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Abstract
Covalently closed circular (ccc) DNA were isolated by a technique involving alkaline denaturation from the spiramycin producer S. ambofaciens KA-1028 and also from spiramycin nonproducing strains AF-11 and QN-25; plasmids could not be detected in these strains by a cleared lysate method. Most of the ccc DNA in these strains was present in the chromosomal and membrane fractions. These ccc DNA had identical mobilities in agarose gel electrophoresis. The size was calculated to be 53.1 .times. 106 daltons from the contour length measurements. The ccc DNA gave 1 fragment on digestion with HindIII, 3 fragments with EcoRI and 28 fragments with BamHI.