title: Characterization of beta-lactamase-deficient (bla) mutants of the R plasmid R1 in Escherichia coli K-12 and comparison with similar mutants of RP1.
abstract: Thirty-eight mutants of R1, an R plasmid specifying the type IIIa (TEM) beta-lactamase, were isolated; these mutants are partially or totally unable to synthesize the type IIIa beta-lactamase. The loss of beta-lactamase activity was associated with a reduction in the level of penicillin resistance conferred by the mutants upon their host strain. At least two of the mutants synthesized a beta-lactamase with altered substrate specificity. These properties are compared with those of two beta-lactamase-deficient mutants of plasmid RP1. The results suggest that, for both R plasmids, penicillin resistance is entirely attributable to the presence of beta-lactamase activity. The properties of two R1 derivatives, pUB251 and pUB252, which have phenotypes similar to that of RP1, support this conclusion.
mesh_terms: D002874:Chromosome Mapping; D003227:Conjugation, Genetic; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D009154:Mutation; D010406:Penicillins / Q000494:pharmacology; D011815:R Factors; D014169:Transformation, Bacterial; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D010406:Penicillins; D001618:beta-Lactamases