title: Mini-Mu insertions in the tetracycline resistance determinant from Proteus mirabilis.
abstract: 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.
authors.affiliation: Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, Universidade Federal de Sö Paulo, Brasil.
authors.forename: V D
authors.initials: VD
authors.lastname: Magalhães
authors.forename: B A
authors.initials: BA
authors.lastname: Castilho
mesh_terms: D000818:Animals; D010583:Bacteriophage mu / Q000235:genetics*; D007763:Lac Operon; D010957:Plasmids / Q000235:genetics*; D011513:Proteus mirabilis / Q000235:genetics*; D013753:Tetracycline Resistance / Q000235:genetics*