Effect of a recD mutation on DNA damage resistance and transformation in Deinococcus radiodurans

Department of Chemistry and Biochemistry and Program in Molecular and Cell Biology, University of Maryland, College Park, MD

^* To whom correspondence should be addressed. Email: djulin{at}umd.edu.

	Abstract

The bacterium Deinococcus radiodurans is resistant to extremely high levels of DNA damaging agents such as ultraviolet light, ionizing radiation, and chemicals such as hydrogen peroxide and mitomycin C. The organism is able to repair large numbers of double-strand breaks caused by ionizing radiation, in spite of the lack of the RecBCD enzyme which is essential for double-strand DNA break repair in Escherichia coli and many other bacteria. The D. radiodurans genome sequence indicates that the organism lacks recB and recC genes, but there is a gene encoding a protein with significant similarity to the RecD protein of E. coli and other bacteria. We have generated D. radiodurans strains with a disruption or deletion of the recD gene. The recD mutants are more sensitive than wild-type cells to irradiation with gamma rays and ultraviolet light, and to treatment with hydrogen peroxide, but they are not sensitive to treatment with mitomycin C and methyl methanesulfonate. The recD mutants also show greater efficiency of transformation by exogenous homologous DNA. These results are the first indication that the D. radiodurans RecD protein has a role in DNA damage repair and/or homologous recombination in the organism.