New nalidixic acid resistance mutations related to deoxyribonucleic acid gyrase activity

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Abstract
In Escherichia coli K-12 mutants which had a new nalidixic acid resistance mutation at .apprx. 82 min on the chromosome map, cell growth was resistant to or hypersusceptible to nalidixic acid, oxolinic acid, piromidic acid, pipemidic acid and novobiocin. DNA gyrase activity as tested by supercoiling of phage .lambda. DNA inside the mutants was similarly resistant or hypersuscpetible 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 phage .lambda. multiplication. Transduction analysis with phage .lambda. carrying the chromosomal fragment of the tnaA-gyrB region suggested that 1 of the mutations, nal-31, was located on the gyrB gene.