title: Selection and characterization of beta-lactam-resistant Escherichia coli K-12 mutants.
abstract: beta-Lactam-resistant mutants of Escherichia coli K-12 were selected by using 12 different beta-lactam derivatives. The mutants fell into three categories showing (i) altered permeation through reduction or loss of outer membrane porin proteins (including ompF, ompR, and envZ alleles); (ii) increase in the rate of synthesis of chromosomally mediated beta-lactamase; or (iii) defective synthesis or action of cyclic adenosine 3',5'-phosphate (cya and crp alleles).
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D009154:Mutation; D001618:beta-Lactamases / Q000096:biosynthesis; D047090:beta-Lactams
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D001618:beta-Lactamases