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New nalidixic acid resistance mutations related to deoxyribonucleic acid gyrase activity
Abstract:
In Escherichia coli K-12 mutants which had a new nalidixic acid resistance mutation at about 82 min on the chromosome map, cell growth was resistant to or hypersusceptible to nalidixic acid, oxolinic acid, piromidic acid, pipemidic acid, and novobiocin. Deoxyribonucleic acid gyrase activity as tested by supercoiling of lambda phage deoxyribonucleic acid inside the mutants was similarly resistant or hypersusceptible to the compounds. The drug concentrations required for gyrase inhibition were much higher than those for cell growth inhibition but similar to those for inhibition of lambda phage multiplication. Transduction analysis with lambda phages carrying the chromosomal fragment of the tnaA-gyrB region suggested that one of the mutations, nal-31, was located on the gyrB gene.
Insights
New mutations in Escherichia coli K-12 confer resistance or hypersusceptibility to quinolones and novobiocin. These mutations affect deoxyribonucleic acid gyrase activity, with nal-31 mapping to the gyrB gene.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Quinolone antibiotics are crucial for treating bacterial infections.
- Understanding resistance mechanisms is vital for effective antibiotic use.
- Escherichia coli K-12 is a model organism for bacterial research.
Purpose of the Study:
- To investigate the effects of novel nalidixic acid resistance mutations in Escherichia coli K-12.
- To characterize the impact of these mutations on bacterial growth and deoxyribonucleic acid gyrase activity.
- To determine the genetic location of the nalidixic acid resistance mutations.
Main Methods:
- Generating and characterizing nalidixic acid-resistant Escherichia coli K-12 mutants.
- Assessing bacterial growth inhibition by various antibiotics.
- Measuring deoxyribonucleic acid gyrase activity via supercoiling assays.
- Utilizing transduction analysis with lambda phages for gene mapping.
Main Results:
- Mutants exhibited altered susceptibility to nalidixic acid, oxolinic acid, piromidic acid, pipemidic acid, and novobiocin.
- Deoxyribonucleic acid gyrase activity in mutants showed resistance or hypersusceptibility to these compounds.
- Drug concentrations for gyrase inhibition differed from those for cell growth inhibition.
- Transduction analysis indicated the nal-31 mutation is located on the gyrB gene.
Conclusions:
- Novel mutations in Escherichia coli K-12 affect both bacterial growth and deoxyribonucleic acid gyrase function.
- The gyrB gene is implicated in the resistance and hypersusceptibility phenotypes observed.
- These findings contribute to understanding quinolone resistance mechanisms.