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The genes regulating resistance to potassium tellurite were cloned from plasmid pS221 with a broad host range. The studied DNA fragment encodes for the synthesis of two polypeptides with molecular mass of 38 and 43 kD. Metal tellurium crystals were localized in the periplasm of Pseudomonas aeruginosa ML4262 (pBS221) cells by electron microscopy. Results of colony hybridization permit us to propose that the cloned genes of potassium tellurite resistance have sites of homology with plasmids RP4(IncP), R27 (IncH), pBS38, pBS79, and R931(IncP-2).

Modern data on prevalence, structural and functional organization of the tetracycline resistance determinants in bacteria are reviewed. The three mechanisms of the antibiotic resistance are the tetracycline efflux, the ribosomal protection and the antibiotic modification. The problems of evolution of tetracycline resistance genes are discussed.

The colony hybridization and tetracycline accumulation techniques made possible to demonstrate the majority of the 29 bacteria of Pseudomonas genera to harbour the plasmids carrying tet determinants belonging to classes A-C, while one strain contained a plasmid carrying tet determinant of class B. For the first time the determinants of classes D and E were found on R plasmids in Pseudomonas aeruginosa. The determinant of G class was identified on two plasmids identical to pBS221 plasmid described previously.