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Deinococcus radiodurans

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Deinococcus radiodurans
521px-Deinococcus radiodurans.jpg
Scientific Classification
Binomial Name

Deinococcus radiodurans

Photomicrograph of Deinococcus radiodurans

Deinococcus radiodurans is a bacteria best known as one of the most radiation-resistant organisms known. Its name basically means 'strange berry that withstands radiation', and the The Guinness Book of Records named it the “World‘s toughest bacterium”.[1] It can tolerate radiation levels at 1000 times the levels that would kill a human and it was originally isolated in 1956 from a can of meat that had been irradiated with X-rays. The bacterium can tolerate high levels of chemical, oxidative, UV, and ionizing radiation-induced damage to the cell's DNA, which it efficiently repairs. The resistance to radiation may reflect its resistance to dessication, which also causes DNA damage.[2]

This organism may be of use in cleaning up toxic metals found at nuclear weapons production sites due to the radiation resistance. The incredibly efficient mechanism for fixing double-strand breaks in the DNA, and the homologous recombination system that utilizes the multiple chromosomal copies, contribute to the radiation tolerance. This bacterium is also a highly efficient transformer, and can readily take up exogenous DNA from the environment, which may also aid DNA repair. This organism carries multiple copies of many DNA repair genes, suggesting a robust system for dealing with DNA damage. The recombination system may rely on multiple copies of various repeat elements found throughout the genome.[3]

The mere existence of D. radiodurans suggests that almost anything is possible.[4]

Anatomy

D. radiodurans photomicrograph showing the tetrad growth unit of this micrococcal eubacteria.

Deinococcus radiodurans are classified as Gram positive bacillus. However, unlike other Gram positive bacillus, it has the outer membrane, which, other negative bacillus should have, and there is a big difference; its outer membrane does not have the heptose and A layer, which is all negative bacillus has. There is no study that has revealed its capacity. It has an absolute resistance against paper radioactivity, ultraviolet, and the peroxide. Speaking of radioactivity, it is fatal for all creatures, because it destroys the dielectric substance of DNA strands.[5]

Genome information

molecule length average ORF length(bp) protein coding regions GC content
chromosomeⅠ 2,648,638 913 90.8% 67.0%
chromosome Ⅱ 412,348 1,044 93.5% 66.7%
megaplasmid 177,499 1,100 90.4% 63.2%
plasmid 45,704 928 80.9% 56.1%
All 3,284,156 937 90.9% 66.6%
[6]

Utility Value of D. Radiodurans

Deinococcus radiodurans are effectively being used to treat cancer. Many DNA try to recover their damaged parts when they become damaged, but when they fail to recover all of the pieces, some of them change to varieties, and most of them would develop to a cancer. Since D. radiodurans have a great ability to treat the cancer, scientists put spurs to use them effectively.

While, NASA and University of Maryland Biotechnology Institute (UMBI) studied together to verify the alien microbe theory, and they sent some microbes to the space which was exposed to the state of vacuum and the sun’s ray. Some of them came back to the earth alive, especially. D. radiodurans, which was uninjured, while other creatures, which stayed alive even after they got back to the earth, died sooner. This experiment provided to the scientists a clue that D. radiodurans are the only living thing that can survive under those conditions. If people have the capacity to resist against radioactivity same as D. radiodurans, then probably people do not have to fear of the end of the earth. Some day, even if humans exterminated, D radiodurans would not be exterminated. John Travis spoke a hopeful mention, “Radiation-resistant bacteria may clean up the nation‘s worst waste side.” It implies that people have a responsibility to turn over the clean earth by preserving it.[7]

Ecology and Discovery

This image is an in vivo non-contact AFM image of the hexagonnally close-packed intermediate (HPI) s-layer of Deinococcus radiodurans, a radiation tolerant bacteria.

In the 1950s, the radioactivity test was used for protecting food. On that experiment, the scientists used the radioactivity, and they discovered a bug, which recovers its DNA in only one day. After they got interested in that microorganism, they prepared several canned meats, and checked the radioactivity: The meats were still rotting, and all of other microbes were completely destroyed, except one microorganism, which is known as deinococcus radiodurans. Afterward, deinococcus radiodurans has been found in some weird places such as Dry Valleys in the South Pole, lake where living things cannot be existed due to the supersaturation of cesium, or in the rocks at the North Pole, which have very strong ultraviolet rays. All these places are unlivable places for people or other creatures.[8][9]

Video

This microorganism is not D. radiodurans, but it shows the movement of D. radiodurans; this microoraganism in this vedeo is basically same as D. radiodurans.

References

External links

  • Wikipedia, the free encyclopedia Deinococcus radiodurans
  • Science Vol.286: 1571-1577 (1999)
  • Nature Biotechnology Oct. 1998

See Also