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Bacteriophage Mu-1-induced mutation to mutT in Escherichia coli
Abstract:
Of approximately 10,000 independent phage Mu-1 lysogens, 3 had a mutator phenotype. One (mutation designated mut-49) resembled mutT1 in the frequency and types of mutations induced. mut-49 was mapped between leu and ace and was not separable from the Mu prophage. mut-49 was recessive and did not complement mutT1. mut-49, like mutT1, did not increase the reversion of the frameshift mutation lac Z (ICR48). mut-49 and mutT1 induced the same two classes of trpA78 revertants, indicating that mut-49 induced adenine-thymine leads to cytosine-guanine transversions. The results support previous work indicating that the mutational specificity of mutT is gene and not allele specific.
Insights
A new bacterial mutator gene, mut-49, was identified in phage Mu-1 lysogens. This mutator causes specific DNA base changes, similar to the known mutT1 mutator, supporting gene-specific mutational effects.
Area of Science:
- Microbiology and Molecular Genetics
- Bacteriophage Research
- DNA Mutagenesis
Background:
- Bacterial mutator genes can alter DNA replication fidelity, leading to increased mutation rates.
- Phage Mu-1 lysogens are potential sources for identifying novel genetic elements affecting bacterial phenotypes.
- The mutT1 gene product is known to induce specific base-pair substitutions.
Purpose of the Study:
- To identify and characterize novel mutator phenotypes arising in independent phage Mu-1 lysogens.
- To compare the mutational characteristics of a newly identified mutator (mut-49) with a known mutator (mutT1).
Main Methods:
- Screening of approximately 10,000 independent phage Mu-1 lysogens for mutator phenotypes.
- Genetic mapping of the mut-49 mutation relative to bacterial genes leu and ace.
- Complementation tests with the mutT1 mutation.
- Analysis of mutation types induced by mut-49 and mutT1 using specific bacterial mutations (lacZ (ICR48) and trpA78).
Main Results:
- Three mutator phenotypes were identified among 10,000 lysogens; one was designated mut-49.
- The mut-49 mutation was mapped between leu and ace, inseparable from the Mu prophage, and was recessive.
- mut-49 did not complement mutT1 and showed similar mutation frequencies and types, including adenine-thymine to cytosine-guanine transversions in trpA78 revertants.
- Neither mut-49 nor mutT1 increased the reversion rate of the lacZ (ICR48) frameshift mutation.
Conclusions:
- A novel mutator gene, mut-49, associated with phage Mu-1, has been identified and characterized.
- mut-49 exhibits mutational specificity similar to mutT1, inducing specific base-pair transversions.
- The findings support the hypothesis that the mutational specificity of mutT is gene-specific, not allele-specific.