Evidence against enhancement of the radioresistance of Escherichia coli by cloned Deinococcus radiodurans DNA

Deinococcus radiodurans genomic DNA, introduced to Escherichia coli in cloning vectors, has been reported to produce radioresistant E. coli that can be selected by gamma irradiation. In this report prior results are reassessed experimentally, and additional studies are presented. Results to date suggest that the acquired radioresistance of E. coli selected by gamma irradiation does not stem from expression of stable plasmid-encoded D. radiodurans sequences, and that acquired radioresistance is not readily transmitted to naive (unirradiated) E. coli by transformation of plasmid recovered from the radioresistant isolates. Several interpretations are discussed.