User:StoutA
A Microbial Biorealm page on the genus StoutA
Classification
Higher order taxa
Bacteria; Deinococcus-Thermus; Deinococci; Deinococcales; Deinococcaaceae [ 1 ]
Species
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NCBI: Taxonomy |
Deinococcus radiodurans
Description and significance
Deinococcus radiodurans is a red-pigmented, non-motile, spherical bacterium 1.5-3.5 µm in diameter. They usually occur as four cells sticking to one another, which is the reason why it carries between 4 and 10 copies of its genome stacked on top of each other, rather than one. The carrying of so many genomes allows them to repair themselves after exposure to radiation, making them the most radiation-resistant organism on Earth. These bacteria are easily to culture because apart from being resistant to radiation, they can also live in extreme conditions; conditions so extreme that their natural habitat is still unknown. D. radiodurans can also withstand dry conditions and a lack of nutrients in the environment, deeming it ‘The World’s Toughest Bacterium”, according to Guinness Book of World Records. Though this organism can survive in extreme conditions, it has been found in nutrient-rich environments, such as soil, animal feces, and processed meats, as well as dry environments like Antarctic Dry Valleys, which is supposed to be extremely relevant to Mars’ environment.
D. radiodurans was originally discovered in a can of ground meat that spoiled after sterilized with radiation. Scientists believe that its ability to repair itself after doses of radiation is similar to its response to dehydration. The physical characteristics and survival mechanisms of D. radiodurans is thought to be possibly applied to environmental cleanup. Though the genes this bacterium possesses is essential to environmental cleanup due to its ability to withstand extreme conditions, genes from other organisms that carry out bioremediation can be injected into D. radiodurans to create a “superbug”. D. radiodurans have also been said to make life more suitable for humans on Mars if they colonize, but this has yet to be proven.
Genome structure
The genome of the R1 strain of D. radiodurans was sequenced in 1999 using whole-genome shotgun sequencing. It is 3,284,156 base pairs long in total and has four major components: chromosome I (2,648,638 base pairs), chromosome II (412,348 base pairs), a megaplasmid (177,466 base pairs), and a small plasmid (45,704 base pairs).
The chromosomes and the megaplasmid contain several genes that allow the bacterium to survive under extreme conditions, including starvation and stress. The bacterium’s genome also reveals a large array of DNA repair mechanisms, including base excision repair, nucleotide excision repair, and mismatch excision repair, all of which exhibit a high amount of redundancy. It is thought that the redundancy of these repair mechanisms explains the bacterium’s ability to resist a variety of mutagens.
Cell structure and metabolism
D. radiodurans is a gram positive, red-pigmented bacterium, usually growing to approximately 1-2μm. Each cell of D. radiodurans exhibits 2 perpendicular furrows that lead to a tetrad structure, and each quarter of the tetrad houses a complete genome. The bacterium is characterized by 6 distinct layers - (from inner to outer) the plasma membrane, the peptidoglycan-containing cell wall (the peptidoglycan layer is 14-20nm thick), the compartmentalized layer, the outer membrane, the electrolucent zone, and the S-layer. Septum formation involves only the cytoplasmic and peptidoglycan layer.
D. radiodurans is an obligatory heterotrophic organism, meaning it requires oxygen to obtain energy from organic materials.
Ecology
Habitat; symbiosis; contributions to the environment.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Current Research
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Cool Factor
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References
Edited by student of Iris Keren
