ISOLATION AND PARTIAL CHARACTERIZATION OF A NEW LINEAR DNA PLASMID ISOLATED FROM BACILLUS-POLYMYXA SCE2

A plasmid, designated pFS1, has been identified for the first time in a strain of Bacillus polymyxa. The plasmid is 16 kb in length. It is s ensitive to digestion by DNAase I, restriction endonucleases and exonu clease III, but resistant to RNAase A and lambda-exonuclease. A restri ction map of the plasmid has been constructed, demonstrating its linea r nature. The linear DNA molecules of pFS1 are attached at their 5' en ds to a protein which can be cleaved by Pronase. No homology was detec ted between pFS1 and chromosomal DNAs from a number of different B. po lymyxa strains. Also, hybridization between pFS1 and total DNA from B. polymyxa SCE2 plasmid-cured derivatives does not occur. The plasmid s eems to be cryptic since B. polymyxa strains harbouring pFS1 and the c ured derivatives have the same phenotype.