Deinococcus geothermalis

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A Microbial Biorealm page on the genus Deinococcus geothermalis

Classification

Higher order taxa

Bacteria; Deinococcus-Thermus; Deinococci; Deinococcales; Deinococcaceae; Deinococcus

Species

Deinococcus geothermalis

Description and significance

Deinococcus geothermalis is a gram-positive, thermophilic radiophile. (1) It was isolated in hot springs in Naples, Italy and in Sao Pedro do Sul in Portugal. D. geothermalis propagates in a temperature range from 45 to 50 °C and a pH range from 4.5 to 8.5, experiencing optimal growth at 47 °C and a pH of 6.5. It forms spherical cells approximately 1.2 to 2.0 micro meters in diameter which amass into orange-pigmented colonies. (2)


Deinococcus geothermalis is capable of reducing Fe (III)-nitrilotriacetic acid, U (VI), and Cr (VI). (1) It is also capable of reducing Hg(II) in the presence of radiation and high temperatures, which was accomplished by transforming it with a plasmid that was designed for Deinococcus radioduran, to produce a "Hg(II)-resistant D. geothermalis strain." (1) It is these characteristics that support the potential development of this bacterium for bioremediation of radioactive waste. (1)

Genome structure

The genome structure of Deinococcus geothermalis is made up of one circular chromosome (2,467,205 base pairs) and a plasmid (574,127 base pairs), producing a genome of 3,041,331 base pairs. (3, 4) Even being exposed to a radiation level of 50 Gy/h D. geothermalis is able to continue its metabolism (1), partly due to the extra copies of its DNA and repair mechanisms available to it. (5)

Cell structure and metabolism

Deinococcus geothermalis is enveloped by a three-layered cytoplasmic membrane, which is enclosed by a cell wall that has a corrugated surface and an electron-dense inner layer. (2) The cell wall enables it to retain a crystal violet dye during the Gram stain, making it a Gram-positive bacterium. (2) During cell division, D. geothermalis divides as tetrads. (2)


Metabolic functions can be carried out with a variety of compounds such as, "casein, gelatin, hide powder azure, hippurate, arbutin, and starch," "D-cellobiose, D-trehalose, lactose, maltose, D-fructose, D-galactose, D-glucose, D-mannose, L-rhamnose, sucrose, Dxylose, D-mannitol, D-sorbitol, glycerol, L-asparagine, L-glutamate, L-glutamine, L-proline, L-serine, malate, pyruvate, and succinate," (2) depending on the specific strain in question.

Ecology

Deinococcus geothermalis does interact with its environment in many different ways; it can form a primary biofilm on abiotic surfaces like industrial printing machines, upon which a secondary biofilm can be formed by another bacterium such as Bacillus. These biofilms on mechanical printing equipment pose a monetary detriment to the printing industry; D. geothermalis can cause defects such as "colored spots" or holes in paper products or impair operation of the machine altogether. (6) It can also serve as bioremediation for radioactive waste products of nuclear weapons by reducing and/or consuming solvents and heavy metals such as toluene and Hg(II). (1, 7)

Application to Biotechnology

Deinococcus geothermalis has the ability to reduce solvents and heavy metals in radioactive sites. This is extremely useful in the bioremediation of radioactive waste. (1) Its bioremedial application is exemplified in the detoxification of radioactive waste, which is generated during the production of nuclear weapons. Researchers were able to produce a strain of Deinococcus geothermalis that is capable of reducing mercury by introducing a plasmid that contained a mercuric reductase gene from Escherichia coli into it (the plasmid was originally engineered for Deinococcus radiodurans). (1,7) Due to Deinococcus geothermalis' radiation resistant nature and genetic manipulation it is capable of detoxifying the ionic mercury in the waste. (7)

Current Research

1. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=169113 - "Engineering Deinococcus geothermalis for Bioremediation of High-Temperature Radioactive Waste Environments"

Deinococcus geothermalis thermophilic, radiation-resistant bacterium. It is related to Deinococcus radiodurans, and has similar reduction capabilities, however D. geothermalis can do so in higher temperatures. D. geothermalis was transformed with a plasmid that was previously engineered for D. radiodurans to reduce Hg(II); this produced a strain of D. geothermalis capable of reducing Hg(II) in 50 Gy/h and in high temperatures. This could yield a thermophilic and extremely radiation-resistant bacterium that is able to treat high-temperature radioactive wastes. (1)

2. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=135001 - "Firm but Slippery Attachment of Deinococcus geothermalis"

Many industrial processes, such as paper mills, are impaired by bacterial biofilms. Deinococcus geothermalis is the initial biofilm former in paper machine water, which acts as a foundation for secondary biofilm bacteria. It forms thick biofilms on abiotic surfaces such as glass, stainless steel, polystyrene, and polyethene; however the mechanism of its attachment is unknown. Utilizing an oscillating probe to "keep the tip-biofilm interactions" small, the atomic force microscopy imaging on D. geothermalis biofilms on water, revealed that cells would not detach but would slide along its surface instead, to avoid the mechanical force. Even detergent and alkali washing of D. geothermalis did not affect its strength of attachment, since it was able to persist for 1 hour. Upon analysis of biofilms produced by D. geothermalis, the cells form a firm but slippery attachment to its surface. (6)

3. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1595522 - "Characterization of Adhesion Threads of Deinococcus geothermalis as Type IV Pili"

As discussed above Deinococcus geothermalis forms biofilms on many industrial machines, such as paper machine surfaces. Cell to cell and cell to surface attachments are mediated by peritrichous appendages, as revealed by field emission electron microscopy. These appendages are "glycosylated type IV pili." This was concluded through various observations of an N-terminal sequence, which showed that the protein of the "extracellular extract" was similar to the "fimbrial protein pilin." Its also similar to "the type IV pilin sequence" of its relative D. radiodurans. The extracellular proteins can be glycosylated. This was reaffirmed through the "periodic acid-Schiff staining for carbohydrates" and confocal laser scanning of D. geothermalis "stained with Amaranthus caudatus lectin, which specifically binds to galactose residues." All of this evidence indicates that D. geothermalis has "glycosylated type IV pili." (8)

References

1. Hassan Brim, Amudhan Venkateswaran, Heather M. Kostandarithes, James K. Fredrickson, and Michael J. Daly, "Engineering Deinococcus geothermalis for Bioremediation of High-Temperature Radioactive Waste Environments" Applied and Environmental Microbiology. 2003 August; Volume 69(8): p. 4575–4582. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=169113

2. Ferreira, A., Nobre, F., Rainey, F., Silva, M., Wait, R., Burghardt, J., Chung, A., Costa, M. "Deinococcus geothermalis sp. nov. and Deinococcus murrayi sp. nov.,Two Extremely Radiation-Resistant and Slightly Thermophilic Species from Hot Springs". International Journal of Systematic Bacteriology. 1997; Volume 47: p. 939-947

3. Peter F. Hallin and David Ussery, CBS Genome Atlas Database: A dynamic storage for bioinformatic results and sequence data Bioinformatics . 2004; Volume 20: p. 3682-3686 https://www.cbs.dtu.dk/services/GenomeAtlas/versions/beta/show-genus.php?KLSO=ASC&KLSK=ORGANISMSORT&kingdom=Bacteria&KLphylaDeinococcusThermus=on&GLgenus=Deinococcus&GLSHWPLA=on&GLSHWMERG=on&GLspecies=geothermalis&GLsupStrain=DSM11300&GLsubStrain=DSM11300

4. Kyoto Encyclopedia of Genes and Genomes. 1995-2007; http://www.genome.jp/kegg-bin/show_organism?org=dge

5. American Society for Microbiology "How "Conan the Bacterium" Survives Lethal Radiation Blasts" Microbeworld. 2006; http://www.microbeworld.org/know/radiation.aspx

6. M. Kolari, U. Schmidt, E. Kuismanen, and M. S. Salkinoja-Salonen, " Firm but Slippery Attachment of Deinococcus geothermalis" Journal of Bacteriology. 2002 May; Volume 184(9): p. 2473–2480 http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=135001

7. "Deinococcus radiodurans" Wikipedia. May 2007; http://en.wikipedia.org/wiki/Deinococcus

8. C. Saarimaa, M. Peltola, M. Raulio, T. R. Neu, M. S. Salkinoja-Salonen, and P. Neubauer "Characterization of Adhesion Threads of Deinococcus geothermalis as Type IV Pili" Journal of Bacteriology. 2006 October; Volume 188(19): p. 7016–7021 http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1595522

Edited by John-Minh Q. Nguyen, student of Rachel Larsen and Kit Pogliano