NOVEL IONIZING RADIATION-SENSITIVE MUTANTS OF DEINOCOCCUS RADIODURANS

Two new loci, irrB and irrI have been identified in Deinococcus radiod urans. Inactivation of either locus results in a partial loss of resis tance to ionizing radiation. The magnitude of this loss is locus speci fic and differentially affected by inactivation of the uvrA gene produ ct. An irrB uvrA double mutant is more sensitive to ionizing radiation than is an irrB mutant. In contrast, the irrI uvrA doable mutant and the irrI mutant are equally sensitive to ionizing radiation. The irrB and irrI mutations also reduce D. radiodurans resistance to UV radiati on, this effect being most pronounced in uvrA(+) backgrounds. Subclone s of each gene have been isolated, and the loci have been mapped relat ive to each other. The irrB and irrI genes are separated by approximat ely 20 kb of intervening sequence that encodes the uvrA and pol genes.