[Phenomenon of the amplification of the determinant of kanamycin resistance (Kanr) in constructed hybrid plasmids in a strain of Streptomyces lividans].

The restriction maps of the hybrid pSU1, pSU2 ..., pSU13 plasmids were constructed. The plasmids are the derivatives of SLP1.2 plasmid and the kanamycin resistance determinant of S. rimosus. Jt was shown that all the 13 hybrid plasmids are capable of tandem reiteration in the genome (amplification) of S. lividans. The conditions for amplification of the hybrid plasmids by one-stage selection of the variants with increased resistance to kanamycin were developed. It was found that the constructed plasmids could be used for cloning and coamplification of additional DNA fragments in them. All the plasmids determined the synthesis of APH(3')--aminoglycoside phosphotransferase responsible for the in-vivo resistance of the strains containing it to neomycin and paromomycin. It is suggested that kanamycin resistance is determined by some other gene and mechanism. An increase in the number of the copies of gene aph1 on amplification resulted in a 50-fold increase in production of APH(3') by it.