Image source: Michael Daly
Bacteria; Deinococcus-Thermus; Deinococci; Deinococcales; Deinococcaceae; Deinococcus; Deinococcus radiodurans
Chromosome 1: 2,648,638 bp
Chromosome 2: 412,348 bp
Plasmid pCP1: 45,704 bp
Plasmid pMP1: 177,466 bp
Deinococcus is a gram-positive bacterium found to form pink or reddish colored colonies. Deinococcus is known for being the most radiation-resistant vegetative cell (R. Murray).
The genome structure of Deinococcus radiodurans is made up of two chromosomes (2,648,638 and 412,348 base pairs), a megaplasmid (177,466 base pairs), and a small plasmid (45,704 base pairs), creating a genome of 3,284,156 base pairs (TIGR, 2004). The megaplasmid and chromosomes qualities are in part what allows the organism to withstand ?-radiation, desiccation, and oxidizing agents as well as many other DNA-damaging conditions such as starvation. D. radiodurans can also grow at 60Gy/h without any growth rate effects being visible (Y. Lui et al., 2003).
When observed by an electron microscope, the cell wall was discovered to have an unusual thickness of about 50-60 nm, with a dense inner layer of about 14-20 nm. This inner wall creates the septa and sometimes the fenestrated layer. The septum forms an unusual shape, described as a pair of curtains rather than the typical "iris-diaphram". Deinococcus typically forms a tetrad shape, allowing a second division to begin before the first is complete during cell division (R. Murray).
The natural habitat of Deinococcus is not yet known because Deinococcus is chemoorganotrophic. It has been isolated from a variety of sites, and needs a complex growth media. It seems that the proteases of Deinococcus may be used for the generation of several useful amino acids and possibly a few sugars as well. Deinococcus strains have been grown from a variety of materials including soil, animal feces, and meat. It is speculated that these aerobic bacteria are likely to live in rich organic habitats, such as feces or intestinal contents (R. Murray).
The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850, USA.
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