Isolation and characterization of four plasmids from Bacillus subtilis

Abstract

Nineteen B. subtilis isolates obtained from type culture collections were examined for the presence of covalently closed circular duplex DNA molecules by the technique of CsCl-ethidium bromide density gradient centrifugation. Four of the 19 strains tested carried covalently closed circular molecules. Two of these strains (IFO3022, IFO3215) harbored a similar plasmid with a MW of 5.4 .times. 106. The other 2 strains (IAM1232, IAM1261) carried 4.9 .times. 106 and 5.3 .times. 106 dalton plasmids, respectively. These plasmid-harboring strains did not show phenotypic traits such as antibiotic resistance or bacteriocin production. The plasmid DNA were digested by 3 restriction endonucleases, EcoRI, HindIII and BamNI, and were classified into 3 different types from their electrophoretic patterns in agarose gels. [The plasmids isolated and characterized in this study should be potentially useful for molecular cloning of DNA in B. subtilis.].