ANTIMUTATOR MUTANTS IN BACTERIOPHAGE-T4 AND ESCHERICHIA-COLI

Antimutators are mutant strains that have reduced mutation rates compa red to the corresponding wild-type strain. Their existence, along with mutator mutants that have higher mutation rates compared to the wild- type strain, are powerful evidence that mutation rates are genetically controlled. Compared to mutator mutants, antimutators have a very dis tinguishing property. Because they prevent normally occurring mutation s, they, uniquely, are capable of providing insight into the mechanism s of spontaneous mutations. In this review, antimutator mutants are di scussed in bacteriophage T4 and the bacterium Escherichia coli, with r egard to their properties, possible mechanisms, and implications for t he sources of spontaneous mutations in these two organisms.