Figure 2. Cell viability is affected under DNA damage in E.coli strains and under conditions in which the SOS response is impaired.

We studied the effect of cell viability at low concentrations of Nalidixic acid (10 µg/ml). E. coli strains WT MC4100relA ⁺ or MC4100relA ⁺ΔclpX or MG1655 or BW25113 were grown to OD₆₀₀ 0.5. We divided each culture into aliquots to which we added no NA (untreated) or added NA 10 µg/ml (treated with NA) or added NA with EDF (treated with NA + EDF) or added NA with iEDF (treated with NA + iEDF) as described in the Legend to Figure 1. We carried out viability assays on LB plates as we have described previously (19).