Photoreactivation in phr mutants of Escherichia coli K-12: cloning from the gal-att lambda interval increases the photoreactivable response in phrA strains.

In this report we have cloned restriction fragments from the gal-att lambda region obtained from a purified preparation of lambda 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 delta 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.