Proliferation of mutators in A cell population.
A Lac- strain of Escherichia coli that reverts by the addition of a G to a G-G-G-G-G-G sequence was used to study the proliferation of mutators in a bacterial culture. Selection for the Lac+ phenotype, which is greatly stimulated in mismatch repair-deficient strains, results in an increase in the percentage of mutators in the selected population from less than 1 per 100,000 cells to 1 per 200 cells. All the mutators detected were deficient in the mismatch repair system. Mutagenesis results in a similar increase in the percentage of mutators. Mutagenesis combined with a single selection can result in a population of more than 50% mutators when a sample of several thousand cells is grown out and selected. Mutagenesis combined with two or more successive selections can generate a population that is 100% mutator. These experiments are discussed in relation to ideas that an early step in carcinogenesis is the creation of a mutator phenotype.
Mao
E F
EF
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024, USA.
Lane
L
L
Lee
J
J
Miller
J H
JH
D004926:Escherichia coli / Q000235:genetics*; D016296:Mutagenesis; D012641:Selection, Genetic