Named the World’s Toughest Bacterium by the Guinness Book of Records, Deinococcus radiodurans translates into “strange berry that withstands radiation”. These bacteria are often called “super bugs” because they can withstand such high levels of radiation. When exposed to 1.7 million rads of radiation, Deinococcus radiodurans can easily repair themselves within a day. This level of radiation is 3,000 times what it takes to kill a human.
The family Deinococcaceae is divided into two genera; Deinobacter which are gram-negative and the Deinococcus which are gram-positive. These extremophiles have been shown to be resistant to ‘genotoxic chemicals, oxidative damage, high levels of ionizing and ultraviolet radiation, and dehydration’. Though, the organism can’t exactly handle heat, it becomes destroyed at 45 degrees centigrade (113 degrees Fahrenheit).
Deinococcus radiodurans was discovered in the 1950s as scientists were experimenting with food sterilization techniques by using radiation (instead of heat) to kill the bacteria and thus preserve food. It was noticed within a canned meat product that something kept growing back after being radiated. Deinococcus is estimated to be over two billion years old and possibly one of the very first forms of life on Earth. Since there is absolutely no reason for organisms to possess such high radiation protection mechanisms on Earth, it is suspected that Deinococcus radiodurans have origins other than Earth. However, due to their low heat tolerances this would have only been possible if a chunk of ice survived the Earths atmosphere.
It has been speculated that Deinococcus radiodurans ability to withstand high radiation is directly related to its ability to survive lengthy periods of dehydration. Dehydration and radiation have similar effects on cell damage in that they both cause double-strand breaks in chromosomal DNA and Deinococcus radiodurans can repair 1000-2000 DNA fragments per cell within 24 hours. Deinococcus radiodurans can do this successfully thanks to redundancy: its genetic code repeats itself many times so that damage in one area can be recognized and quickly repaired (Conan the Bacterium, SpaceDaily, December 1999).
Deinococcus is also being studied for medicinal purposes, toxic waste cleanup, and in the search for exterestrial life, namely on Mars. “Deinococcus radiodurans beats most of the constraints for survival of life on Mars - radiation, cold, vacuum, dormancy, oxidative damage, and other factors," said Dr. Robert Richmond, a research biologist at NASA's Marshall Space Flight Center (Conan the Bacterium, SpaceDaily, December 1999). If anything could survive on Mars, it would most likely be Deinococcus radiodurans and by studying this unique specimen we can better speculate living conditions on Mars as well as environmental conditions of ancient Earth.
Another major application of Deinococcus radiodurans is waste cleanup due to its amazing abilities to withstand radiation. Although Deinococcus radiodurans does not consume toxic waste on its own accord, mutant strains have been created in laboratories for such purposes.
“Waste-eating bacteria have been used successfully in toxic waste cleanup, but all known strains cannot survive in a radioactive environment. Researchers Michael Daly of the Uniformed Services University of the Health Sciences, Larry Wackett at the University of Minnesota, and Jim Fredrickson of Pacific Northwest National Laboratory have teamed to construct a recombinant strain of Deinococcus radiodurans that could survive a mixed waste environment and degrade the organic chemicals to a less toxic state (Conan the Bacterium, SpaceDaily, December 1999).
References:
Bacteria Museum, Deinococcus radiodurans
http://www.bacteriamuseum.org/species/Dradiodurans.shtmlWitches’ Brew of Weird Bugs, National Science Foundation, October 1996
http://www.nsf.gov/news/frontiers_archive/10-96/10bugs.jspWorld’s Toughest Bacterium Has a Taste for Waste, Rosalind Schrempf, Pacific Northwest National Laboratory, August 1998
http://www.pnl.gov/er_news/08_98/art2.htmResearchers Develop Munching Bacteria, Jake Kapsner, The Minnesota Daily, October 1998
http://www.mndaily.com/daily/1998/10/21/news/munch/Conan the Bacterium, Huntsville, SpaceDaily.Com, December 1999
http://www.spacedaily.com/news/life-99l.htmlDeinococcus radiodurans, Tim Lottman
http://web.umr.edu/~microbio/BIO221_2000/Deinococcus_radiodurans.html”Weird Life” Almost Better than Fiction, Annette Trinity-Stevens, Montana State University, March 2000
http://www.montana.edu/wwwpb/univ/weird.html
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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