BEHAVIOR OF HETEROLOGOUS RECOMBINANT PLAS MID PCET IN CELLS OF BACILLUS-ANTHRACIS

Recombinant plasmid pCET was constructed in vivo in cells of enteric a nd hay bacillus, on the basis of plasmids pC194, pE194, and pBC16. Pla smid pCET inherits marker genes of antibiotic resistance from parental plasmids. Anthrax cells were transformed by the recombinant plasmid d eveloped. The behavior of this plasmid was studied in vegetative Bacil lus anthracis cells, which did not pass through the sporulation stage and were cultivated at temperatures permissive for the replicon of pla smid pE194. Under these conditions, plasmid pCET was shown to replicat e autonomously, regardless of the host chromosome, and to retain its s tructure, irrespective of the recipient strain. In this case, the phen otype of transformants fully corresponded to the genotype of plasmids inherited. Elevation of the cultivation temperature of strains Bac. an thracis (pCET) up to 44 degrees C led to the elimination of plasmid pC ET from cells of anthrax microbe under conditions nonselective for pla smid pCET and its integration with the host chromosome under selective conditions. The frequency of plasmid pCET integration into the chromo some was approximately 10(-1) for all Bac. anthracis strains studied. In populations of vegetative cells of strains Bac. anthracis (pCET), w hich passed through the sporulation stage under selective for plasmid pCET conditions, DNA of plasmid pCET was detected only in the state in tegrated with the chromosome. Irrespective of the reasons leading to t he integration of plasmid pCET into the Bac. anthracis chromosome, all strains inheriting this DNA within their own genome lost the resistan ce to tetracycline observed in strains with the extrachromosomal plasm id location. Genome amplification of plasmid pCET in the chromosome of Bac. anthracis was detected.