[Hyperrecombination of plasmids is characteristic for hyperresistant strains of Escherichia coli]

Intraplasmid recombination frequency was assessed in several Escherichia coli K12 strains by the kinetic bioluminescence method. Enhanced plasmid recombination was observed in two mutant E. coli K12 strains, which were hyperresistant to DNA-damaging agents, gamma-rays, photosensitizer 8-methoxypsoralen. Plasmid recombination frequency per one generation (P) was calculated. In mutant strains, this value was shown to exceed that in control isogenic strains with a standard resistance approximately by a factor of 15. Enhanced constitutive synthesis of specific proteins such as heat-shock proteins in Gamr444 and a 55-kDa protein in SA270 in hyperresistant mutant strains is assumed to promote activity of the recombinational RecF pathway system.