Survival of DH5α complemented with various pUC18-recA constructs after UV irradiation. ▪, pUC18-recAEc; ♦, pUC18-recABb; □, pUC18; ⋄, pUC18-recABb: Kmr. The enhanced survival of pUC18-recAEc- or pUC18-recABb-complemented E. coli at a UV dose of 4,000 μJ/cm2 relative to the survival of pUC18-complemented E. coli was statistically significant at a P value of 0.002 (indicated by asterisks).