PNNL

Abstract

The whole-genome sequence of Deinococcus geothermalis is the second for an extremely ionizing radiation (IR) resistant bacterium. The first was for Deinococcus radiodurans, which for 50 years has been the subject of extensive investigations aimed at solving the mystery of how this microbe can survive immense doses of ?-rays. So far, comparative analyses between the genome of D. radiodurans and genomes of other bacteria have failed to produce a coherent picture of the underlying resistance systems. Most surprisingly, many critical DNA repair genes identified in D. radiodurans are present in sensitive bacteria, whereas the involvement of many uncharacterized genes implicated in resistance by transcriptome analyses has not been borne out by mutant studies. Genomic subtraction of D. geothermalis from D. radiodurans was used to define a minimal gene set for extreme resistance, whereby unique genes were ruled out, and shared genes were pooled as candidates for resistance. We revise down substantially the number of potential genetic determinants of extreme radiation resistance, identify a putative regulator and a palindromic binding site for genes which comprise a distinct Deinococcus radiation response regulon, and consider the impact of those findings on the prevailing models of extreme radiation resistance.