Loss of the hyperrec phenotype in strains expressing RecA D112R protein.

The second column documents ΔFRE, the relative increase in the frequency of genetic exchange per chromosomal DNA unit length (ΔFRE is a ratio of the FRE observed with the indicated strain divided by FRE for comparable cells expressing the wild type RecA protein), after continuous culture for 70 cell generations. The third column shows results obtained after the plasmids from the cultured strains were isolated and used to again transform strain JC10289. Four of the plasmids (from cultures 8, 11, 12, and 13) still produce an elevated ΔFRE. In the final column, the strains were cured of their resident plasmid, and re-transformed with pRecA D112R. The lower ΔFRE scores in some of these strains reflect the effects of chromosomal mutations.