Natural plasmid pSD89 (Cm~r) from Salmonella derby K89 enhanicing radiation resistance of Escherichia coli K-12 strains

摘要

Several plasmids with molecular mass of 1.3-9 MDa were found in a clinical isolate of Salmonella derby K89 by electrophoresis in agarose gel. One of these plasmids, designated pSD89, was derived from the K89 strain via transformation of the plasmidless recipient S. derby K82 to chloramphenicol resistance. The plasmidcarrying strain K89 and the K82 strain completely cured of plasmids were equally sensitive to the lethal action of UV light, whereas the plasmid-carrying strain was even more sensitive to ionizing radiation than the plasmidless variant. Nevertheless, transformants carrying only plasmid pSD89 were found to be more resistant to #gamma#-rays and UV light than the recipient. By using an intermediate host Excherichia coli Z80. plasmid pSD89 was introduced into different E. coli K-12 strains: polA~-, recA~-, uvrA~-, umuC~- and the wild type strain. A slight increase in radioresistance of E. coli wild-type cells and a significant complementation of a repair defect in recA and polA mutants, but not in uvrA and umuC, were observed.