Thermotolerant nalidixic acid-resistant mutants ofEscherichia coli |
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Authors: | Dr. S. Marvin Friedman Mary L. Droffner Nobuto Yamamoto |
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Affiliation: | (1) Department of Microbiology and Immunology, Hahnemann University School of Medicine, Philadelphia, Pennsylvania, USA;(2) Department of Biological Sciences, Hunter College of the City University of New York, 695 Park Avenue, 10021 New York, NY, USA |
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Abstract: | Nalidixic acid-resistant mutants ofEscherichia coli CGSC #6353 capable of growth at 48°C were obtained by mutagenesis withN-methyl-N-nitro-N-nitrosoguanidine. Cotransductional analyses employing phage P1 indicated that the mutation resulting in the phenotype of growth at 48°C is an allele of thegyrA structural gene. Similar thermal inactivation kinetics were observed for ribosomes isolated from a thermotolerant (T/r) mutant grown at both 37°C and 48°C and from the parental strain grown at 37°C. Cell-free extracts prepared from the T/r mutant grown at 48°C exhibited a sharp increase in protein synthesis at 55°C, whereas this effect was not displayed by extracts from the mutant or parental strains grown at 37°C. In addition, preincubation at 55°C enhanced protein synthesis at 37°C up to 15-fold in an extract prepared from the T/r mutant grown at 48°C, whereas comparable values were 2.6- to 3.0-fold for extracts from the mutant and parental strains grown at 37°C. |
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