Are Escherichia coli dam- as compared to dam+ hypermutable by base analogs?

It was shown that some base analogs, like n2Pur and n2oh6Ade (but not n2om6Ade or oh4Cyd) which strongly inhibit growth of dam- cells, mutagenize and preselect dam- populations. As a result dam- mut(-)--devoid of mismatch repair, dam+ revertants, or dam(-)--insensitive to a base analog are exclusively obtained after mutagenesis. The composition of these mutants depends on the base analog applied. By using reconstruction experiments, the frequency of these mutations induced by n2Pur was calculated.