Mini-Mu insertions in the tetracycline resistance determinant from Proteus mirabilis
Magalhães, V.D.; Castilho, B.A.
Brazilian Journal of Medical and Biological Research 30(3): 363-367
1997
ISSN/ISBN: 0100-879X PMID: 9246234 Document Number: 470711
The inducible tetracycline resistance determinant isolated from Proteus mirabilis cloned into the plasmid pACYC177 was mutagenized by insertion of a mini-Mu-lac phage in order to define the regions in the cloned sequences encoding the structural and regulatory proteins. Three different types of mutants were obtained: one lost the resistance phenotype and became Lac+; another expressed the resistance at lower levels and constitutively; the third was still dependent on induction but showed a lower minimal inhibitory concentration. The mutant phenotypes and the locations of the insertions indicate that the determinant is composed of a repressor gene and a structural gene which are not transcribed divergently as are other known tetracycline determinants isolated from Gram-negative bacteria.