A new bacteriocinogenic activity: Megacin BII encoded by plasmid pSE 203 in strains of Bacillus megaterium

Mesophilic strains producing a new bacteriocin: Megacin BII, have been isolated from strains of Bacillus megaterium. Facultatively thermophilic strains producing Megacin BI were less sensitive to this new activity than nonproducing mesophiles and strains producing Megacin BII were also also more resistant to Megacin BI. Strains producing Megacin BII contained a large plasmid of 36·10⁶:pSE 203. This plasmid was introduced into non-megacinogenic acceptor strains by protoplast transformation, they then became megacin producers and immune to Megacin BII. Plasmid pSE 203 has been mapped with endonucleases. No similarity to the Megacin A plasmids pBM 309 [Rostás et al. (1980) and pBM 113 (von Tersch and Carlton (1983b)] was evident.Abbreviations CFU colony forming units - CCO covalently closed circular - OC open circular - LIN linear - EB ethidium bromide - Meg megacin - Tris tris (hydroxyl methyl) amino methane - Ot obligately thermophilic - Ft facultatively thermophilic - Sm streptomycin - Trim trimethoprim - Rif rifampicin - Thy thymine - Tc tetracycline