Genomic organization of the radioresistant bacteriumDeinococcus radiodurans: physical map and evidence for multiple replicons

A physical map of Deinococcus radiodurans strain KD8301 was constructed by ordering DNA fragments from genomic DNA digested with the enzymes NotI and PmeI. NotI produced 13 fragments and PmeI four fragments. Junction fragments and multiple enzyme digestion of the genomic DNA, in conjunction with Southern hybridization analysis indicated that KD8301 contains chromosome I (2.6 megabases), chromosome II (0.4 megabases) and an endogenous plasmid (0.2 megabases). DNA repair genes such as recA, uvrA, polA and ruvB were found on chromosome I. The lexA gene was on chromosome II. Pulsed-field gel electrophoresis analysis of undigested DNA indicated that monomer and multimer forms of chromosome II existed in cells. These results suggested that the mechanisms involved in multimer formation may serve as a system for radioresistance of this bacterium.