Deinococcus radiodurans Totally Explained

Everything about Deinococcus Radiodurans totally explained

Deinococcus radiodurans is an extremophilic bacterium, one of the most radioresistant organisms known. It can survive cold, dehydration, vacuum, and acid, and is therefore known as a polyextremophile and has been listed as "the world's toughest bacterium" in The Guinness Book Of World Records.

Name and classification

The name "Deinococcus radiodurans" means "terrifying berry that withstands radiation". The species was formerly also called Micrococcus radiodurans and Deinobacter radiodurans. As a consequence of its hardiness it has been nicknamed "Conan the Bacterium".
Initially it was placed in the genus Micrococcus. After evaluation of ribosomal RNA sequences and other evidence, it was placed in its own genus Deinococcus, which is closely related to the genus Thermus of heat-resistant bacteria; the group consisting of the two is accordingly known as Deinococcus-Thermus. Deinococcus is the only genus in the order Deinococcales. D. radiodurans is the type species of this genus, and the best studied member. All known members of the genus are radioresistant: D. proteolyticus, D. radiopugnans, D. radiophilus, D. grandis, D. indicus, D. frigens, D. saxicola, D. marmola, D. geothermalis and D. murrayi; the latter two are also thermophilic.

History

D. radiodurans was discovered in 1956 by A.W. Anderson at the Oregon Agricultural Experiment Station in Corvallis, Oregon. Experiments were being performed to determine if canned food could be sterilized using high doses of gamma radiation. A tin of meat was exposed to a dose of radiation that was thought to kill all known forms of life, but the meat subsequently spoiled. D. radiodurans was isolated from the meat.
   The complete DNA sequence of D. radiodurans was published in 1999 by TIGR. A detailed annotation and analysis of the genome appeared in 2001. D. radiodurans doesn't form endospores and is nonmotile. It is an obligate aerobic chemoorganoheterotroph, for example it uses oxygen to derive energy from organic compounds in its environment. It is often found in habitats rich in organic materials, such as soil, feces, meat, or sewage, but has also been isolated from dried foods, room dust, medical instruments and textiles. In addition to DNA repair, D. radiodurans use LEA (Late Embryogenesis Abundant) protein expression to protect against desiccation. Scanning electron microscopy analysis has shown that DNA in D. radiodurans is organized into tightly packed toroids, which may facilitate DNA repair.
   A team of Croatian and French researchers have bombarded D. radiodurans to study the mechanism of DNA repair. At least two copies of the genome, with random DNA breaks, can form DNA fragments through annealing. Partially overlapping fragments are then used for synthesis of homologous regions through a moving D-loop that can continue extension until they find complementary partner strands. In the final step there's crossover by means of RecA-dependent homologous recombination.
   Michael Daly has suggested that the bacterium uses manganese as an antioxidant to protect itself against radiation damage. In a 2008 his team showed that high intracellular levels of manganese(II) in D. radiodurans protect proteins from being oxidized by radiation, and proposed the idea that "protein, rather than DNA, is the principal target of the biological action of [ionizingradiation] in sensitive bacteria, and extreme resistance in Mn-accumulating bacteria is based on protein protection".
   A team of Russian and American scientists proposed that the radioresistance of D. radiodurans had a Martian origin. Evolution of the microorganism could have taken place on the Martian surface until it was delivered to Earth on a meteorite. It has been hypothesised that such objects might have attained sufficient kinetic energy to achieve escape velocity as a result of a major meteorite impact on the Martian surface (this being part of a hypothesised process known as panspermia). The heating effects of that impact and of entry into the Earth's atmosphere would have had to have been insufficient to sterilise such an object. However, apart from its resistance to radiation, Deinococcus is genetically and biochemically quite similar to other terrestrial life forms, arguing against an extraterrestrial origin.

Applications

Using genetic engineering Deinococcus has been used for bioremediation to consume and digest solvents and heavy metals, even in a highly radioactive site. The bacterial mercuric reductase gene has been cloned from Escherichia coli into Deinococcus to detoxify the ionic mercury frequently found in radioactive waste generated from nuclear weapons manufacture. Those researchers developed a strain of Deinococcus that could detoxify both mercury and toluene in mixed radioactive wastes.
The Craig Venter Institute has used a system derived from the rapid DNA repair mechanisms of D. radiodurans to assemble synthetic DNA fragments into chromosomes, with the ultimate goal of producing a synthetic organism they call Mycoplasma laboratorium.
In 2003, U.S. scientists demonstrated that D. radiodurans could be used as a means of information storage that might survive a nuclear catastrophe. They translated the song It's a Small World into a series of DNA segments 150 base pairs long, inserted these into the bacteria, and were able to retrieve them without errors 100 generations later.

Trivia

The computer game Anarchy Online features an item called Deinococcus radiodurans which is used to make a "stim" (potion) that reduces damage from radioactive sources.
Michael Flynn's short story "The Washer at the Ford" has as its major plot point the development of a radiation "innoculation", comprised of nanomachines with a DNA repair mechanism inspired by Deinococcus radiodurans (referred to by its old name M. Radiodurans).

Further Information

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