Photoreactivation in phr mutants of Escherichia coli k-12: Cloning from the gal-attλ interval increases the photoreactivable response in phrA strains

In this report we have cloned restriction fragments from the gal-attλ region obtained from a purified preparation of λ dgal transducing 'phage DNA, and demonstrate the appearance of a photoreactivable response in a photoreactivation-deficient phrA phrB strain. We also show that when this plasmid is transduced into a Δ phrA strain there is an increase in the photoreactivable response after a single high intensity light flash and after continuous illumination. These data have been discussed in relation to the hypothesis of the presence of multiple photolyase molecules in Escherichia coli.