Difference between revisions of "PMID:1715857"

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{|  id="B4f8882b23ae6f"  class=" tableEdit PMID_info_table" 
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'''Hächler, H, Cohen, SP and Levy, SB'''  (1991) marA, a regulated locus which controls expression of chromosomal multiple antibiotic resistance in Escherichia coli.''J. Bacteriol.'' '''173''':5532-8
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!align=left  |Abstract
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Stable chromosomal multiple-antibiotic-resistant (Mar) mutants of Escherichia coli, derived by exposing susceptible cells to low concentrations of tetracycline or chloramphenicol, express cross-resistance to structurally unrelated antibiotics. The entire resistance phenotype is reversed to susceptibility by insertion of transposon Tn5 into a locus, designated marA, near 34 min on the chromosome (A. M. George and S. B. Levy, J. Bacteriol. 155:541-548, 1983). Strains in which 39 kbp of chromosomal DNA, including marA, had been deleted were unable to produce Mar mutants. The deletion strain could be complemented in trans by introduction of intact marA+ on plasmid F'506. Junction fragments from a strain containing marA::Tn5 were cloned, exploiting kanamycin resistance on Tn5 for selection. They were used as probes to search a phasmid library of E. coli K-12 for recombinants containing the marA+ region. Two phasmids which contained regions hybridizing to this probe were identified and shown to complement delta marA in a deletion strain. From one phasmid, several marA-containing fragments were cloned: those of greater than or equal to 7.8 kbp restored the ability to form Mar mutants in a deletion strain. These Mar mutants were shown to be dependent on the cloned marA fragment. Chromosomal as well as recombinant Mar mutants showed increased expression of a marA-specific mRNA species of about 1.4 kb, which was barely or not detectable in wild-type strains. Exposure of mutants and, to a lesser extent, parental strains to tetracycline or chloramphenicol resulted in elevated levels of mRNA which hybridized to the marA probe. These results indicate that the marA locus is needed for production of Mar mutants and is regulated, responding to at least two antibiotics to which it controls resistance.
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[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1715857 PubMed]
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Autoradiography; Chromosome Mapping; Chromosomes, Bacterial; Cloning, Molecular; DNA, Bacterial; Drug Resistance, Microbial; Escherichia coli; Gene Expression Regulation, Bacterial; Genes, Bacterial; Mutation; Nucleic Acid Hybridization; Phenotype; RNA, Bacterial; Restriction Mapping; Transcription, Genetic
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==Main Points of the Paper ==
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{{LitSignificance}}
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== Materials and Methods Used ==
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{{LitMaterials}}
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==Phenotype Annotations==
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==Notes==
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==References==
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[[Category:Publication]]

Revision as of 14:46, 13 April 2012

Citation

Hächler, H, Cohen, SP and Levy, SB (1991) marA, a regulated locus which controls expression of chromosomal multiple antibiotic resistance in Escherichia coli.J. Bacteriol. 173:5532-8

Abstract

Stable chromosomal multiple-antibiotic-resistant (Mar) mutants of Escherichia coli, derived by exposing susceptible cells to low concentrations of tetracycline or chloramphenicol, express cross-resistance to structurally unrelated antibiotics. The entire resistance phenotype is reversed to susceptibility by insertion of transposon Tn5 into a locus, designated marA, near 34 min on the chromosome (A. M. George and S. B. Levy, J. Bacteriol. 155:541-548, 1983). Strains in which 39 kbp of chromosomal DNA, including marA, had been deleted were unable to produce Mar mutants. The deletion strain could be complemented in trans by introduction of intact marA+ on plasmid F'506. Junction fragments from a strain containing marA::Tn5 were cloned, exploiting kanamycin resistance on Tn5 for selection. They were used as probes to search a phasmid library of E. coli K-12 for recombinants containing the marA+ region. Two phasmids which contained regions hybridizing to this probe were identified and shown to complement delta marA in a deletion strain. From one phasmid, several marA-containing fragments were cloned: those of greater than or equal to 7.8 kbp restored the ability to form Mar mutants in a deletion strain. These Mar mutants were shown to be dependent on the cloned marA fragment. Chromosomal as well as recombinant Mar mutants showed increased expression of a marA-specific mRNA species of about 1.4 kb, which was barely or not detectable in wild-type strains. Exposure of mutants and, to a lesser extent, parental strains to tetracycline or chloramphenicol resulted in elevated levels of mRNA which hybridized to the marA probe. These results indicate that the marA locus is needed for production of Mar mutants and is regulated, responding to at least two antibiotics to which it controls resistance.

Links

PubMed

Keywords

Autoradiography; Chromosome Mapping; Chromosomes, Bacterial; Cloning, Molecular; DNA, Bacterial; Drug Resistance, Microbial; Escherichia coli; Gene Expression Regulation, Bacterial; Genes, Bacterial; Mutation; Nucleic Acid Hybridization; Phenotype; RNA, Bacterial; Restriction Mapping; Transcription, Genetic

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.
<protect>

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

</protect>

Notes

References

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