Deinococcus radiodurans

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Deinococcus radiodurans
Deinococcus radiodurans.jpg

Deinococcus radiodurans

Systematics
Domain : Bacteria (bacteria)
Department : Deinococcus Thermus
Order : Deinococcales
Genre : Deinococcus
Type : Deinococcus radiodurans
Scientific name
Deinococcus radiodurans
(ex Raj et al. 1960) Brooks and Murray 1981

The Deinococcus radiodurans (formerly as Micrococcus radiodurans referred to) is a polyextremophiles bacterium that against ionizing radiation is resistant even in very high doses. It belongs to the gram-positive cocci , but has a cell wall typical of gram- negative bacteria. The lipid A contained in the gram-negative cell wall is missing.

resistance

D. radiodurans is still able to grow and thrive at chronic (long-term) radiation doses of 60  Gy per hour. The mean lethal dose LD 50 , i.e. the acute (short-term) radiation dose that statistically leads to death in 50 percent of the exposed organisms, is over 10,000 Gy for these bacteria, some of the organisms even survive acute radiation doses of up to 17,500 Gy. For comparison: with acute radiation from 6 Gy without massive medical intensive care, people have little chance of survival (up to 90% lethality ); with radiation doses of 7–10 Gy, 100 percent of those affected die within one to two weeks (LD 100/14 ). See also the article radiation sickness .

Because of its properties, it is also called Conan, the bacterium , after the film hero of the same name from Conan the Barbarian , who escaped the almost inevitable death several times.

discovery

Deinococcus radiodurans was discovered by Arthur W. Anderson in 1956 when canned meat was treated with ionizing radiation to kill germs. The bacterium was not killed by the rather high, but by its own standards comparatively low, radiation dose and was then examined in more detail. A previously unknown resistance to ultraviolet and X-rays was found.

distribution

Deinococcus radiodurans and its close relatives are proverbial generalists and globetrotters: In addition to canned meat, they can also be found in tissues from Atlantic haddock , lama faeces , Antarctic rocks and other inhospitable places. Together with cyanobacteria of the species Chroococcidiopsis , they form a special group of organisms that are able to thrive under the harshest living conditions ( extremophiles ). They are able to find ecological niches even in the most hostile places in the world , and are therefore ubiquitous , including in the cooling water circuit of nuclear reactors and in the intestines of humans.

Genome

The genome of D.radiodurans consists of 4 circular molecules:

It is believed that chromosome II is essential for the organism.

Radiation resistance

The main reason for the extreme radiation resistance against ionizing radiation is the ability to defective DNA repair exceptionally efficient. DNA and parts of chromosomes caused by mutagens such as radiation , chemical attack or accidental causes damage suffered are, with the help of certain enzymes particularly quickly and effectively repaired again. This repair mechanism even allows double-strand breaks, a particularly severe form of DNA damage, to be repaired . In this way, Deinococcus radiodurans is able to carry out 500 such repairs at the same time, while the intestinal bacterium Escherichia coli , for example, only manages two to three. D. radiodurans has four copies of the genome in the stationary phase and eight to ten copies during exponential growth. Other bacteria also have multiple genome copies ( Micrococcus luteus , Micrococcus sodonensis ), but these are radiation-sensitive. Therefore, the multiplicity of the genome alone has no influence on radiation resistance. So far, the molecular factors that make this unusual repair work possible have not yet been adequately clarified. The DNA, which is arranged in the form of a ring, plays a role here, preventing the pieces of genetic material broken out by radiation from being washed away in the cell fluid.

In addition, the bacterium has a very strong cell wall , which also protects it from UV radiation.

Another extremely radiation-resistant bacterium is the halophilic Halobacterium sp. NRC-1, of which there are mutants that survive acute radiation doses of up to 11,000 Gy.

meaning

Astrobiology

For astrobiologists looking for traces of extraterrestrial life, survivors like Deinococcus radiodurans and Chroococcidiopsis are of great interest, as it is conceivable that such organisms hidden in meteorite rocks could survive long journeys through space unharmed . This would strengthen the panspermia hypothesis , which states that simple life forms are able to move across the universe over great distances. Some could have found their way to earth around 3.5 billion years ago and thus formed the origin of life on this planet.

Information technology

Their special resistance to damaging effects of all kinds could make Deinococcus radiodurans interesting for use as a data storage device in information technology . Research is currently being carried out into how data in the form of artificial DNA can be stored in the bacteria and retrieved again. American computer scientists translated the text of the English nursery rhyme It's a Small World into the genetic code and smuggled the corresponding DNA sequence into the genetic material of the bacteria. Even after about a hundred generations of bacteria, the stanzas could be read out again in unchanged form using standard sequencing technology , i.e. That is, the information introduced was stored in a stable manner and, in addition, the multiplication of the bacteria increased their redundancy.

literature

Web links

Individual evidence

  1. ↑ KS Makarova, L Aravind, YI Wolf, RL Tatusov, KW Minton, EV Koonin, MJ. Daly: Genome of the extremely radiation-resistant bacterium Deinococcus radiodurans viewed from the perspective of comparative genomics. In: Microbiol Mol Biol Rev. Volume 65 , no. 1 , March 2001, p. 44-79 , PMID 11238985 .
  2. ↑ MJ Daly, KW. Minton: Recombination between a resident plasmid and the chromosome following irradiation of the radioresistant bacterium Deinococcus radiodurans. In: Genes . tape 187 , no. 2 , March 1997, p. 225-229 , PMID 9099885 .
  3. ↑ a b Lukas Wieselberg: Radiation resistant: Conan, the bacterium. In: science.ORF.at. January 2003, accessed on July 21, 2014 (Based on Ringlike Structure of the Deinococcus radiodurans Genome: A Key to Radioresistance? In: Science (Volume 299, p. 254)).
  4. ^ Patrick Huyghe: Conan the Bacterium . In: The Sciences . New York Academy of Sciences, July 1998, pp. 16–19 (English, usuhs.edu [PDF; accessed July 25, 2014]).
  5. ↑ EM Bik, PB Eckburg, SR Gill, KE Nelson, EA Purdom, F. Francois, G. Perez-Perez, MJ Blaser, DA Relman: Molecular analysis of the bacterial microbiota in the human stomach . In: Proceedings of the National Academy of Sciences of the United States of America . tape 103 , no. 3 , January 17, 2006, p. 732-737 , PMID 16407106 .
  6. ↑ a b R. Froböse: When frogs fall from the sky: the craziest natural phenomena. Wiley-VCH, Weinheim 2007, ISBN 978-3-527-31659-5 , p. 19 ff. ( [1] ).
  7. ↑ Owen White et al .: Genome Sequence of the Radioresistant Bacterium Deinococcus radiodurans R1 . In: Science . tape 286 , no. 5444 , November 19, 1999, p. 1571-1577 .
  8. ↑ M Blasius, S Sommer, U. Hübscher: Deinococcus radiodurans: what belongs to the survival kit? In: Crit Rev Biochem Mol Biol. Volume 43 , no. 3 , 2008, p. 221-228 , PMID 18568848 .
  9. ↑ Harsojo, S. Kitayama, A. Matsuyama: Genome multiplicity and radiation resistance in Micrococcus radiodurans . In: Journal of Biochemistry . tape 90 , no. 3 , 1981, p. 877-880 , PMID 7309705 .
  10. ↑ LC DeVeaux, JA Müller, J Smith, J Petrisko, DP Wells, S. DasSarma: Extremely radiation-resistant mutants of a halophilic archaeon with increased single-stranded DNA-binding protein (RPA) gene expression . In: Radiat Res . tape 168 , no. 4 , October 2007, p. 507-514 , PMID 17903038 .
  11. ↑ B. Diaz et al .: Microbial survival rates of Escherichia coli and Deinococcus radiodurans under low temperature, low pressure, and UV-Irradiation conditions, and their relevance to possible Martian life. In: Astrobiology. Volume 6, No. 2, April 2006, pp. 332-347, PMID 16689650 .
  12. ↑ Comparative Survival Analysis of D. radiodurans, N. magadii, and H. volcanii Exposed to Vacuum Ultraviolet Irradiation . spaceref.com, accessed October 5, 2011.
  13. ↑ Radiation-resistant bacteria as permanent data storage. In: Netzeitung . January 10, 2003, archived from the original on February 11, 2013 ; Retrieved February 11, 2009 .