The mechanism of the extreme radioresistance in Deinococcus radiodulance

As for the mechanism of the extreme radioresistance of the title bacterium (Dr), authors reviewed recent findings on its DNA repair enzyme genes together with its biological character. In evolution, Dr is close to Thermus bacteria. Radiation energy necessary for breakage of intracellular DNA strand is similar to each other in Dr and E.coli, however, Dr can repair such breakage as lethal in other bacteria. Genes of recA, pprA, lexA homologue, recA/pprA expression-inducing, recN, ruvB, polA, recRDNA, uvrA and uvde homologue were identified as those concerning the DNA repair enzyme in wild type and mutant strains of Dr. Authors found the presence of polymeric structure of its genome, which suggesting that Dr highly evolved the DNA recombination capability. Dr would have the additional ones as well as the DNA repair mechanisms known in other bacteria like E. coli. Analyses of recA and pprA genes which were found in the highly radiation-sensitive strain, and of their regulator genes would bring about the further new knowledge. (K.H.)