154. Complete Genome Sequence of Deinococcus radiodurans 

Owen White, John Heidelburg, Claire Fraser, and J. Craig Venter 
The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20855 
owhite@tigr.org 

Deinococcus radiodurans is a non-pathogenic, non-sporulating, red-pigmented Gram+ bacterium. D. radiodurans was originally found in radiation sterilized food that under went spoilage. It is remarkable in that it is the most radioresistant organism to have ever been isolated (Moseley, 1983). An important component of this resistance is the ability to repair damage to chromosomal DNA. D. radiodurans cultures exposed to 1.5 Mrad of radiation displayed reduction in size of genomic DNA fragments corresponding to approximately 100 double stranded breaks (DSBs) per genome. (Typically, most prokaryotic and eukaryotic organisms cannot tolerate more than 5 double stranded breaks per genome without reduced survival.) Remarkably, within eight to ten hours after exposure, D. radiodurans genomic fragment lengths are restored to size ranges seen in non-treated cells. During this repair time, cellular replication of D. radiodurans is arrested (Daly et al., 1994); however, after this eight to ten hour interval, the cells display 100% survival with no detectable mutagenesis of their completely restored genomes. The genome sequence of Deinococcus is complete and we have determined the genome is composed of 3 chromosomes and a small plasmid; a number of unique sequence elements have been identified. The content of the genome, along experimental results will be discussed in context of this organism's unique ability to withstand gamma radiation.