From OMPwiki
Jump to: navigation, search

Normark, S and Burman, LG (1977) Resistance of Escherichia coli to penicillins: fine-structure mapping and dominance of chromosomal beta-lactamase mutations. J. Bacteriol. 132:1-7


Seven Escherichia coli K-12 mutants with a lowered chromosomal beta-lactamase activity were analyzed genetically. The beta-lactamase-negative mutants isolated from ampA1-carrying strains (resistant to 10 microgram of ampicillin per ml) all carried genetic lesions very close to the ampA1 mutation, which was still present. In an earlier report, two of the mutations mediating a beta-lactamase-negative phenotype (L. G. Burman, T. Park, E. B. Linström, and H. G. Boman, J. Bacteriol. 116:123-130, 1973) were shown to have occurred in the structural gene for beta-lactamase, designated ampC. It is suggested that all beta-lactamase-negative mutants studied here were altered in ampC. The relative order of ampC mutations was (ampC1, ampC8)-ampC9-(ampC12, ampC14)-ampC11, and the gene order was found to be ampC-1mpA-purA. The ampA1 allele was dominant over its wild-type allele but acted only cis and not trans, suggesting that ampA is the promoter or operator region for ampC. A gene dosage effect was found for strains homozygous for ampA+ ampC+ or ampA1 ampC+. Heterozygotes carrying the ampC8 allele on the chromosome showed an apparent derepression of the episomal ampC allele, suggesting a role for beta-lactamase in its own regulation.


PubMed PMC221818


Alleles; Ampicillin/pharmacology; Chromosome Mapping; Conjugation, Genetic; Diploidy; Escherichia coli/drug effects; Escherichia coli/enzymology; Escherichia coli/genetics; Genes, Dominant; Mutation; Penicillin Resistance; Penicillinase/biosynthesis; Penicillinase/genetics; Penicillinase/metabolism; Plasmids

Main Points of the Paper

Please summarize the main points of the paper.

Materials and Methods Used

Please list the materials and methods used in this paper (strains, plasmids, antibodies, etc).

Phenotype Annotations

See Help:AnnotationTable for details on how to edit this table.

Phenotype of Taxon Information Genotype Information (if known) Condition Information OMP ID OMP Term Name ECO ID ECO Term Name Notes Status



See Help:References for how to manage references in OMPwiki.