NEW MATERIAL:A cyclic plasmid of about 51.5kb, separated from oxetanocin- producing Bacillus megaterium NK84-0218 strain, cleavable with a restriction enzyme PstI without being cleavable with restriction enzyme NotI, XhoI and SmaI and providing DNA fragments of 25kb, 11kb, 9.5kb and 6.0kb. USE:For molecular biological breeding of oxetanocin-producing microorganisms. PREPARATION:For example, Bacillus megaterium NK84-0218 strain is cultured in a culture medium, centrifuged at a low speed to collect bacterial cells, which are then suspended in a buffer solution. A lysozyme is subsequently added to treat the suspension and a surfactant is then added, and allows the resulting mixture to stand in a 3M sodium acetate solution under conditions of cooling with ice. The obtained mixture is subsequently centrifuged and phenol is added to the resultant supernatant. Thereby, proteins are denatured and removed. Ethanol is then added to precipitate DNA, which is separated and redissolved. Ethidium bromide and cesium chloride are added to carry out centrifugation and afford the objective plasmid.
