Deinococcus radiodurans

Literally a "radiation hardened terrible ball." This is an appropriate name.

D. radiodurans was first isolated in 1956 from a radiation "sterilized" can of ground meat. It seems to be a widespread organism, but is a weak competitor and consequently is only cultured from samples that have been subjected to extreme treatments.

Gram positive, red pigmented, nonmotile coccus.

Lethal dose of ionizing radiation for humans is roughly 5 Gy (Gray; one Gray = 100 rad). Cultures of Deinococcus can be exposed to 5000-30,000 Gy and still survive. This dose is sufficient to break the genome into many fragments, but Deinococcus has mechanisms that permit it to reassemble even severely fragmented chromosomes.

Phylogenetic analyses of SSU rRNA had placed it on a long branch close to Thermus aquaticus, a thermophilic bacterium, but the validity of this placement had been questioned.

In 1999 the complete genome sequence of D. radiodurans R1 was determined by TIGR.

Four genetic elements:

White et al., 1999. Genome sequence of the radioresistant bacterium Deinococcus radiodurans R1. Science 286:1571-1576.

Daly, M.J. and Minton, K.W. 1995. Resistance to radiation. Science 270:1318.