[Molecular cloning of chlortetracycline resistance gene from chlortetracycline producer Streptomyces aureofaciens].

The chlortetracycline (CT) resistance gene ctr was cloned from S. aureofaciens 633, a strain producing the antibiotic. The 6.6-kb DNA Bam HI fragment containing the resistance gene was cloned with the plasmid vector pIJ699. Comparison of the restriction maps of the cloned gene and the oxytetracycline (OT) resistance gene otrA from S. rimosus revealed their similarity which enabled identification of the cloned resistance gene as otrA. Investigation of the resistance determinants in S. aureofaciens 633 made it possible to identify a mtr gene(s). It was demonstrated that introduction of a ctrA gene into S. lividance provided a simultaneous increase in the resistance of the recipient strain to CT and a number of macrolide antibiotics. The CT resistance determinants in S. lividans TK64 showed properties of exogenous induction by CT and the macrolide antibiotics similar to the properties of the mtr gene(s) of S. aureofaciens. Possible adaptation properties of mtr genes are discussed.