DOE Microbial Genome Program Report
Super Survivor Deinococcus radiodurans
Although the ability of the lowly cockroach to withstand radiation has long been admired, it is far surpassed by that of the bacterium Deinococcus radiodurans. Scientists are eager to learn how D. radiodurans thrives in massive amounts of radiation and how to exploit this property to clean up mixed-waste sites around the world, a legacy resulting from nuclear weapons production between 1945 and 1986. Researchers are adding genes from other species to D. radiodurans to increase its ability to remediate radioactive sites containing such metallic and organic contaminants as mercury and toulene.
Electron photomicrograph of D. radiodurans (sequenced in the DOE Microbial Genome Program, typically found as a cluster of four cells (a tetrad). D. radiodurans and related species have been identified worldwide, including in Antarctic granite and in water-shielding tanks of powerful 60Cobalt irradiators in Denmark. [Image and graph data by the Deinococcus team (Uniformed Services University of the Health Sciences]
|The radiation-resistance profile of D. radiodurans compared to such other organisms as the common intestinal bacterium Escherichia coli, cockroaches, and humans. When older colonies of D. radiodurans are used, their survival extends much farther, to around 17kGy (1.7 million rads). Scientists believe this extreme radiation resistance may be a side effect of D. radiodurans' ability to survive severe dehydration, which also fragments DNA. [Nature Biotechnology 18, 85-90 (January 2000)] [Image and graph data by the Deinococcus team (Uniformed Services University of the Health Sciences]|
Deinococcus radiodurans: The Ultimate Assembly Machine
The upper panel depicts DNA fragments extracted from D. radiodurans cells after high doss of radiation. The lower panel shows an intact, repaired DNA molecule hours later. Both panels depict "optical maps" of molecules viewed on a slide through an optical light microscope. Understanding the remarkable DNA-repair mechanisms of D. radiodurans may offer insights into some human cancers caused by DNA damage. [photos provided by David Schwartz (University of Wisconsin, Madison)]
| D. radiodurans 1.75 million
rads, 0 h
D. radiodurans 1.75 million rads, 24 h
[photos provided by David Schwartz (University of Wisconsin, Madison)]
Ordered restriction map (colored circle) and optical of a single circular 415,000-base (415-kb) DNA molecule snipped apart using a special DNA-cutting protein, the restriction enzyme Nhe I. Circular DNA elements are difficult to identify using nonoptical approaches, since these molecules break and become linear elements. Optical mapping generates a picture of the entire genome's architecture, revealing the number of chromosomes and the existence of extrachromosomal elements. This technique was critical to the discovery that D. radiodurans has four chromosomal elements rather than just one.
|The online presentation of this 2000 publication is a special feature of the Human Genome Project Information Web site.|