Figure 1.

Genetic characterization of B. fragilis addAB. (a) Serial dilutions of E. coli cultures were spotted onto LB plates and irradiated with ultraviolet light (+UV). The viability of the ΔrecBCD strain is greatly reduced upon exposure, compared to the wild type, but can be rescued by expression of addAB. Expression of either addA or addB, or the presence of the plasmid vector pTRC99a, did not affect sensitivity to ultraviolet light. (b) Serial dilutions of B. fragilis cultures spotted onto BHI-S plates. Deletion of addAB from B. fragilis increased sensitivity of the bacterium to UV compared to the wild-type strain.