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Properties of mitomycin C-sensitive mutants of Escherichia coli K-12
Abstract:
Strains hypersensitive to mitomycin C (MC) were isolated from Escherichia coli K-12 after treatment with nitrosoguanidine. Of 43 MC-sensitive strains tested for their ultraviolet light (UV) sensitivity and for their ability to reactivate UV-inactivated lambda phage, 38 were found to be insensitive to UV irradiation and to be able to reactivate UV-irradiated bacteriophage lambda. Some properties of the MC-sensitive, uvr(+) mutants were analyzed. Synthesis of deoxyribonucleic acid (DNA) in MC-sensitive, uvr(+) mutants was inhibited at a lower concentration of MC than in the wild-type strain. Mutant cells, labeled with (3)H-thymidine and then exposed to MC, released radioactivity as low molecular weight compounds. The amount of radioactivity released was the same as that from the wild-type strain. MC-sensitive, uvr(+) mutants, as well as the corresponding wild-type strain, were equally susceptible to induction of prophage phi80 by UV irradiation. However, MC induction of prophage was achieved in MC-sensitive, uvr(+) mutants at a lower concentration of the antibiotic than in the wild-type strain. Genetic experiments indicated that a gene controlling MC sensitivity is located close to that determining lactose fermentation of E. coli. It is situated on episome F'13, and the wild type is dominant to the MC-sensitive allele.
Insights
New Escherichia coli strains sensitive to mitomycin C (MC) were identified. These strains exhibit altered DNA synthesis and prophage induction responses, suggesting a specific genetic basis for MC sensitivity.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Mitomycin C (MC) is an antibiotic with DNA-damaging properties.
- Understanding mechanisms of DNA repair and mutagenesis is crucial in microbial genetics.
- Escherichia coli serves as a model organism for studying DNA repair pathways.
Purpose of the Study:
- To isolate and characterize mitomycin C (MC)-sensitive mutants of Escherichia coli.
- To investigate the relationship between MC sensitivity, UV sensitivity, and phage reactivation.
- To analyze the genetic basis and phenotypic properties of MC-sensitive mutants.
Main Methods:
- Induction of mutations in Escherichia coli K-12 using nitrosoguanidine.
- Screening for mitomycin C (MC)-sensitive strains.
- Assessing UV sensitivity and the ability to reactivate UV-inactivated bacteriophage lambda.
- Analyzing deoxyribonucleic acid (DNA) synthesis inhibition by MC.
- Measuring prophage induction by MC and UV irradiation.
- Genetic mapping of the MC sensitivity gene on an episome.
Main Results:
- 38 out of 43 MC-sensitive strains were UV-resistant and capable of reactivating UV-inactivated lambda phage.
- MC-sensitive, uvr(+) mutants showed inhibited DNA synthesis at lower MC concentrations.
- Mutant cells released low molecular weight compounds upon MC exposure, similar to wild-type.
- MC induction of prophage phi80 occurred at lower MC concentrations in sensitive mutants.
- The MC sensitivity gene was mapped to episome F'13, with the wild-type allele being dominant.
Conclusions:
- MC-sensitive, uvr(+) mutants possess distinct DNA metabolism characteristics.
- These mutants provide insights into DNA repair pathways and MC-induced responses.
- The genetic locus for MC sensitivity is linked to lactose fermentation genes on episome F'13.