The DNA excision repair system of the highly radioresistant bacterium Deinococcus radiodurans is facilitated by the pentose phosphate pathway

Deinococcus radiodurans is highly resistant to radiation and mutagenic chemicals. Mutants defective in the putative glucose-6-phosphate dehydrogenase gene (zwf(-)) and the aldolase gene (fda(-)) were generated by homologous recombination. These mutants were used to test the cells' resistance to agents that cause dimer formation and DNA strand breaks. The zwf(-) mutants were more sensitive to agents that induce DNA excision repair, such as UV irradiation and H2O2, but were as resistant to DNA strand break-causing agents such as methylmethanesulphonic acid (MMS) and mitomycin C (MMC) as the wild-type cells. Analysis of the cytoplasmic fraction of zwf(-) cells showed that the concentrations of inosine monophosphate (IMP) and uridine monophosphate (UMP) were only 30% of those found in the wild-type cells. The fda(-) mutants were slightly more resistant to UV light and H2O2. Results suggested that the deinococcal pentose phosphate pathway augmented the DNA excision repair system by providing cells with adequate metabolites for the DNA mismatch repair.