Deinococcus radiodurans

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Deinococcus radiodurans
A tetrad of D. radiodurans
Scientific classification Edit this classification
Domain: Bacteria
Phylum: Deinococcota
Class: Deinococci
Order:
Deinococcales
Family:
Deinococcaceae
Genus: Deinococcus
Species:
D. radiodurans
Binomial name
Deinococcus radiodurans
Brooks & Murray, 1981
Look up Deinococcus  or radiodurans in Wiktionary, the free dictionary.

Deinococcus radiodurans is a

bacterium, an extremophile and one of the most radiation-resistant organisms known. It can survive cold, dehydration, vacuum, and acid, and therefore is known as a polyextremophile. The Guinness Book Of World Records listed it in January 1998[1] as the world's most radiation-resistant bacterium or lifeform.[2]

Name and classification

The name Deinococcus radiodurans derives from the Ancient Greek δεινός (deinos) and κόκκος (kokkos) meaning "terrible grain/berry" and the Latin radius and durare, meaning "radiation surviving". The species was formerly called Micrococcus radiodurans. As a consequence of its hardiness, it has been nicknamed “Conan the Bacterium”, in reference to Conan the Barbarian.[3]

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.[4]

Deinococcus is one genus of three 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. marmoris, D. deserti,[5] D. geothermalis, and D. murrayi; the latter two are also thermophilic.[6]

History

D. radiodurans was discovered in 1956 by Arthur Anderson at the

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, and D. radiodurans was isolated.[1]

The complete

The Institute for Genomic Research. A detailed annotation and analysis of the genome appeared in 2001.[4]
The sequenced strain was ATCC BAA-816.

Deinococcus radiodurans has a unique quality in which it can repair both

double-stranded DNA. When damage is apparent to the cell, it brings the damaged DNA into a compartmental ring-like structure where the DNA is repaired, and then is able to fuse the nucleoids from the outside of the compartment with the damaged DNA.[8]

In August 2020, scientists reported that

space dust, meteoroids, asteroids, comets, planetoids, or contaminated spacecraft.[9][10]

Description

D. radiodurans is a rather large, spherical bacterium, with a diameter of 1.5 to 3.5

Gram negative bacteria.[12]

Deinococcus radiodurans does not form

chemoorganoheterotroph, i.e., it uses oxygen to derive energy from organic compounds in its environment. It is often found in habitats rich in organic materials, such as sewage, meat, feces, or, soil, but has also been isolated from medical instruments, room dust, textiles, and dried foods.[12]

It is extremely resistant to ionizing radiation, ultraviolet light, desiccation, and oxidizing and electrophilic agents.[13]

PCR assays and Fluorescent in Situ Hybridization (FISH) techniques can be used to test for D. radiodurans in nature.[citation needed]

Its genome consists of two circular chromosomes, one 2.65 million base pairs long and the other 412,000 base pairs long, as well as a megaplasmid of 177,000 base pairs and a plasmid of 46,000 base pairs. It has approximately 3,195 genes. In its stationary phase, each bacterial cell contains four copies of this genome; when rapidly multiplying, each bacterium contains 8-10 copies of the genome.[citation needed]

Ionizing-radiation resistance

Deinococcus radiodurans is capable of withstanding an acute dose of 5,000 grays (Gy), or 500,000 rad, of ionizing radiation with almost no loss of viability, and an acute dose of 15,000 Gy with 37% viability.[14][15][16] A dose of 5,000 Gy is estimated to introduce several hundred double-strand breaks (DSBs) into the organism's DNA (~0.005 DSB/Gy/Mbp (haploid genome)). For comparison, a chest X-ray or Apollo mission involves about 1 mGy, 5 Gy can kill a human, 200–800 Gy will kill E. coli, and more than 4,000 Gy will kill the radiation-resistant tardigrade.[citation needed]

Several bacteria of comparable radioresistance are now known, including some species of the genus Chroococcidiopsis (phylum cyanobacteria) and some species of Rubrobacter (phylum Actinomycetota); among the archaea, the species Thermococcus gammatolerans shows comparable radioresistance.[6] Deinococcus radiodurans also has a unique ability to repair damaged DNA. It isolates the damaged segments in a controlled area and repairs it. These bacteria can also repair many small fragments from an entire chromosome.[8]

Mechanisms of ionizing-radiation resistance

Deinococcus accomplishes its resistance to radiation by having multiple copies of its

single-stranded annealing. In the second step, multiple proteins mend double-strand breaks through homologous recombination. This process does not introduce any more mutations than a normal round of replication would. Theoretically, Deinococcus should have little or even no mutation accumulation.[citation needed
]

Scanning electron microscopy analysis has shown that DNA in D. radiodurans is organized into tightly packed toroids, which may facilitate DNA repair.[17]

A team of Croatian and French researchers led by

annealing. Partially overlapping fragments are then used for synthesis of homologous regions through a moving D-loop that can continue extension until the fragments find complementary partner strands. In the final step, there is crossover by means of RecA-dependent homologous recombination.[18]

Deinococcus radiodurans is capable of genetic transformation, a process by which DNA derived from one cell can be taken up by another cell and integrated into the recipient genome by homologous recombination.[19] When DNA damages (e.g. pyrimidine dimers) are introduced into donor DNA by UV irradiation, the recipient cells efficiently repair the damages in the transforming DNA, as they do in cellular DNA, when the cells themselves are irradiated.

Michael Daly has suggested the bacterium uses manganese complexes as antioxidants to protect itself against radiation damage.[20] In 2007 his team showed that high intracellular levels of manganese(II) in D. radiodurans protect proteins from being oxidized by radiation, and they proposed the idea that "protein, rather than DNA, is the principal target of the biological action of [ionizing radiation] in sensitive bacteria, and extreme resistance in Mn-accumulating bacteria is based on protein protection".[21] In 2016, Massimiliano Peana et al. reported a spectroscopic study through NMR, EPR, and ESI-MS techniques on the Mn(II) interaction with two peptides, DP1 (DEHGTAVMLK) and DP2 (THMVLAKGED), whose amino acid composition was selected to include the majority of the most prevalent amino acids present in a Deinococcus radiodurans bacterium cell-free extract that contains components capable of conferring extreme resistance to ionizing radiation.[22] In 2018, M. Peana and C. Chasapis reported by a combined approach of bioinformatic strategies based on structural data and annotation, the Mn(II)-binding proteins encoded by the genome of DR and proposed a model for Manganese interaction with DR proteome network involved in ROS response and defense. [23]

A team of Russian and American scientists proposed that the radioresistance of D. radiodurans had a Martian origin. They suggested that evolution of the microorganism could have taken place on the Martian surface until it was delivered to Earth on a meteorite.[24] However, apart from its resistance to radiation, Deinococcus is genetically and biochemically very similar to other terrestrial life forms, arguing against an extraterrestrial origin not common to them.

In 2009, nitric oxide was reported to play an important role in the bacteria's recovery from radiation exposure: the gas is required for division and proliferation after DNA damage has been repaired. A gene was described that increases nitric oxide production after UV radiation, and in the absence of this gene, the bacteria were still able to repair DNA damage, but would not grow.[25]

Evolution of ionizing-radiation resistance

A persistent question regarding D. radiodurans is how such a high degree of radioresistance could evolve. Natural

primordial radionuclides not yet having decayed and due to effects of things like the natural nuclear fission reactors at Oklo, Gabon, which were active some 1.7 billion years ago. However, even if adaptations to such conditions did evolve during that time, genetic drift would almost certainly have eliminated them if they provided no (other) evolutionary benefit.[citation needed
]

Valerie Mattimore of

Late Embryogenesis Abundant proteins)[27] expression to protect against desiccation.[28]

In this context, also the robust S-layer of D. radiodurans through its main protein complex, the S-layer Deinoxanthin Binding Complex (SDBC), strongly contributes to its extreme radioresistance. In fact, this S-layer acts as a shield against electromagnetic stress, as in the case of ionizing radiation exposure, but also stabilizes the cell wall against possible consequent high temperatures and desiccation.[29][30]

Applications

Deinococcus radiodurans as a model system for studying the cell cycle

Deinococcus radiodurans has been shown to have a great potential to be used in different fields of investigation. Not only has D. radiodurans been genetically modified for bioremediation applications, but also it has been discovered that it could perform a major role in biomedical research and in nanotechnology.

cloned from Escherichia coli into Deinococcus to detoxify the ionic mercury residue frequently found in radioactive waste generated from nuclear weapons manufacture.[31] Those researchers developed a strain of Deinococcus that could detoxify both mercury and toluene in mixed radioactive wastes. Moreover, a gene encoding a non-specific acid phosphatase from Salmonella enterica, serovar Typhi,[32] and the alkaline phosphatase gene from Sphingomonas[33]
have been introduced in strains of D. radiodurans for the bioprecipitation of uranium in acid and alkaline solutions, respectively.

In the biomedical field, Deinococcus radiodurans could be used as a model to study the processes that lead to

aging and cancer.[34] Some lines of investigation are focused on the application of D. radiodurans antioxidant systems in human cells to prevent ROS damaging and the study of the development of resistance to radiation in tumoral cells.[35]

A nanotechnological application of D. radiodurans in the synthesis of

antifouling effects, and cytotoxicity
to tumoral cells.

Moreover, there are other uncommon applications of Deinococcus radiodurans. The

chromosomes, with the ultimate goal of producing a synthetic organism they call Mycoplasma laboratorium.[38] In 2003, U.S. scientists demonstrated 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 bacterial generations later.[39]

Clues for future search of extremophile microbial life on Mars

When cultured and exposed to ionizing radiations in liquid media, Deinococcus radiodurans could survive up to 25 kGy.

Rosalind Franklin rover, it would be necessary to target a relatively young impact crater to increase the chances of discovering dormant extremophile micro-organisms surviving in the dry and frozen Martian subsurface environment relatively protected from the lethal ionizing radiations.[40]

See also

References

  1. ^ a b "Most radiation-resistant lifeform". Guinness World Records. Archived from the original on June 23, 2015. The red-coloured bacterium Deinococcus radiodurans can resist 1.5 million rads of gamma radiation, about 3,000 times the amount that would kill a human. The bacteria was first isolated from cans of meat that were subjected to supposedly sterilising doses of radiation in the megarad range.
  2. ^ DeWeerdt, Sarah E. (July 5, 2002). "The World's Toughest Bacterium". Genome News Network. The Center for the Advancement of Genomics. Archived from the original on May 6, 2003. Deinococcus radiodurans is listed in the Guinness Book of World Records as "the world's toughest bacterium."
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  40. ^ a b Cooper, Keith (25 October 2022). "Extremophiles on Mars could survive for hundreds of millions of years". Space.com. Retrieved 28 October 2022.
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External links
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