1887

Abstract

In a single copy of Tn10 confers high-level resistance to tetracycline. Resistance itself results from expression of three distinct mechanisms which normally act together ( Shales ., 1980 ). In cells containing two copies of Tn10, the level of resistance to tetracycline was reduced. This was not due to overproduction of the repressor which controls the resistance genes, because strains diploid for an operator-constitutive allele of Tn10 also exhibited reduced expression of resistance. The negative gene dosage effect resulted from decreased expression of two mechanisms (1 and 2) consequent on enhanced expression of the third mechanism. The net result of increasing the copy number was a decrease in resistance because mechanism 3 was less efficient than mechanisms 1 and 2 in protecting the cell against tetracycline. The DNA sequence responsible for the reduced expression of resistance was contained in the internal II fragment of Tn10. This sequence, which is probably unique to Tn10, may encode the protein which mediates mechanism 3. Elevated levels of this protein probably cause decreased expression of mechanisms 1 and 2.

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1981-09-01
2024-04-27
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References

  1. Achtman M., Willetts N., Clark A. J. 1971; Beginning a genetic analysis of conjugational trans-fer determined by the F factor in Escherichia coli by isolation and characterization of transfer-deficient mutants. Journal of Bacteriology 106:529–538
    [Google Scholar]
  2. Ball P. R., Shales S. W., Chopra I. 1980; Plasmid-mediated tetracycline resistance in Escherichia coli involves increased efflux of the antibiotic. Biochemical and Biophysical Research Communications 93:74–81
    [Google Scholar]
  3. Beck C. F. 1979; A genetic approach to the analysis of transposons. Proceedings of the National Academy of Sciences of the United States of America 762376–2380
    [Google Scholar]
  4. Cabello F., Timmis K., Cohen S. N. 1976; Replication control in a composite plasmid con-structed by in vitro linkage of two distinct replicons. Nature, London 259:285–290
    [Google Scholar]
  5. Chopra I., Howe T. G. B. 1978; Bacterial resistance to the tetracyclines. Microbiological Reviews 42:707–724
    [Google Scholar]
  6. Chopra I., Ball P. R., Eccles S. J., Shales S. W. 1981; Nature and function of TnlO-encoded proteins that mediate tetracycline resistance in Escherichia coli. . In Molecular Biology, Pathogenicity, and Ecology of Bacterial Plasmids in the Press Edited by Levy S. B. New York: Plenum Publishing Corp;
    [Google Scholar]
  7. Foster T. J. 1977; Isolation and characterisation of mutants of R100-1 which express tetracycline resistance constitutively. FEMS Microbiology Letters 2:271–274
    [Google Scholar]
  8. Foster T. J., Howe T. G. B., Richmond K. M. V. 1975; Translocation of the tetracycline resistance determinant from R100-1 to the Escherichia coli chromosome. Journal of Bacteriology 124:1153–1158
    [Google Scholar]
  9. Jorgensen R. A., Reznikoff W. S. 1979; Organization of structural and regulatory genes that mediate tetracycline resistance in transposon TnlO. Journal of Bacteriology 138:705–714
    [Google Scholar]
  10. Jorgensen R. A., Berg D., Reznikoff W. 1978; Genetic organization in the transposable tetracycline resistance determinant Tn10. In Microbiology - 1978 pp. 181–183 Edited by Schlessinger D. Washington, D.C.: American Society for Microbiology;
    [Google Scholar]
  11. Jorgensen R., Berg D., Allet B., Reznikoff W. 1979; A restriction endonuclease cleavage map for the transposable tetracycline resistance determinant Tn10. Journal of Bacteriology 137:681–685
    [Google Scholar]
  12. Levy S. B., Mcmurry L. 1978; Probing the expression of plasmid-mediated tetracycline resistance in Escherichia coli. . In Microbiology - 1978 pp. 177–180 Edited by Schlessinger D. Washington, D.C.: American Society for Microbiology;
    [Google Scholar]
  13. Levy S. B., Mcmurry L., Onigman P., Saunders R. M. 1977; Plasmid-mediated tetra-cycline resistance in Escherichia coli. . In Topics in Infectious Diseases 2 pp. 181–203 Edited by Drews J., Hogenauer G. New York: Springer Verlag;
    [Google Scholar]
  14. Mattes R., Burkardt H. J., Schmitt R. 1979; Repetition of tetracycline resistance determinant genes on R plasmid pRSDl in Escherichia coli. . Molecular and General Genetics 168:173–184
    [Google Scholar]
  15. Mendez B., Tachibana C., Levy S. B. 1980; Heterogeneity of tetracycline resistance determi-nants. Plasmid 3:99–108
    [Google Scholar]
  16. Nordstrom K., Ingram L. C., Lundback A. 1972; Mutations in R factors of Escherichia coli causing an increased number of R-factor copies per chromosome. Journal of Bacteriology 110:562–569
    [Google Scholar]
  17. Schmitt R., Bernhard E., Mattes R. 1979; Characterisation of Tnl721, a new transposon containing tetracycline resistance genes capable of amplification. Molecular and General Genetics 172:53–65
    [Google Scholar]
  18. Shales S. W., Chopra I., Ball P. R. 1980; Evidence for more than one mechanism of plasmid- determined tetracycline resistance in Escherichia coli. . Journal of General Microbiology 121:221–229
    [Google Scholar]
  19. Tay10r D. P., Greenberg J., Rownd R. H. 1977; Generation of miniplasmids from copy number mutants of the R plasmid NR 1. Journal of Bacteriology 132:986–995
    [Google Scholar]
  20. Uhlin B. E., Nordstrom K. 1975; Plasmid incompatibility and control of replication: copy mutants of the R-factor R1 in Escherichia coli. . Journal of Bacteriology 124:641–649
    [Google Scholar]
  21. Uhlin B. E., Nordstrom K. 1977; R plasmid gene dosage effects in Escherichia coli K-12: copy mutants of the R plasmid R1 drd-19. Plasmid 1:1–7
    [Google Scholar]
  22. Ward J. M., Grinsted J. 1978; Mapping of functions in the R-plasmid R388 by examination of deletion mutants generated in vitro. . Gene 3:87–95
    [Google Scholar]
  23. Yang H. L., Zubay G., Levy S. B. 1976; Synthesis of an R plasmid protein associated with tetracycline resistance is negatively regulated. Proceedings of the National Academy of Sciences of the United States of America 731509–1512
    [Google Scholar]
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