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The characteristics of eleven mutants of R-factor R57 constitutive for tetracycline resistance, selected and tested in Escherichia coli K12

Published online by Cambridge University Press:  14 April 2009

E. C. R. Reeve
Affiliation:
Institute of Animal Genetics, West Mains Road, Edinburgh EH9 3JN, Scotland
J. M. Robertson
Affiliation:
Institute of Animal Genetics, West Mains Road, Edinburgh EH9 3JN, Scotland

Summary

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Eleven mutants of R-factor R57 have been isolated which show constitutive expression of resistance to tetracycline (Tc). These derepressed (Tdr) mutants all gave a much greater resistance to Tc and to its analogue, minocycline, than could be obtained by optimal induction of cells carrying the wild-type (T+) determinant. Cells carrying each of the Tdr mutants together with T+ of either R6-S or of a plasmid found in Escherichia coli mi19 showed inducible Tc resistance, indicating that the Tdr mutants were all recessive, i.e. of repressor-negative type. Tdr1 was not recessive to the T-determinant of RP1, suggesting that the repressor gene products of the T-determinants in R57 and RP1 have different specificities.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1975

References

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