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Methanococcoides burtonii
''Methanococcoides burtonii'' is a methylotrophic methanogenic archaeon first isolated from Ace Lake, Antarctica. Its type strain is DSM 6242.
''Methanococcoides burtonii'' is an extremophilic archeon of the family ''Methanosarcinaceae'', a family of three genera of coccus-shaped cells. ''Methanococcides burtonii'' has adapted to life in Antarctica where it resides in Ace Lake at temperatures that remain permanently 1-2 °C.〔 ''M. burtonii'' was first discovered by an Austrian limnologist named Harry Burton.〔 It was determined that the optimal temperature of growth was 23 °C.〔 ''M. burtonii'' is able to grow on methylated substrates and tolerates a broad range of growth temperatures (< 4° to 29 °C).〔 The cold adaptation in ''M. burtonii'' involves specific changes in membrane lipid unsaturation and flexible proteins. ''M. burtonii'' are irregular cocci, ranging 0. to 1.8 micrometers in diamter.〔 ''M. burtonii'' occur singly or in pairs.〔 During Gram staining, cells lysej; they also lyse in hypotonic solutions.〔 ''M. burtonii'' are motile with a single flagellum, and lack storage structures and internal membranes in the cytoplasm.〔 ''M. burtonii'' are colony-forming archaea, usually occurring in <1 millimeter colonies that are circular and convex.〔 Cells of ''M. burtonii'' fluoresce blue when exposed to UV illumination.〔 The optimal initial pH for growth is 7.7.〔 Two substances found to stimulate growth are yeast extract and trypticase soy agar.〔 ''M. burtonii'' cells were found to be resistant to penicillin, ampicillin, tetracycline, vancomycin and erythromycin.〔 Although it has evolved the ability to sustain itself in what are considered "extremophilic" environments for archaea (1-2 °C), ''M. burtonii'' optimally grows at 23 °C. ''M. burtonii'' is an obligately methylotrophic methanogen able to use methylamines and methanol, but not formate, H2CO2, or acetate for growth.〔 Methane is a greenhouse gas, and methanogens play a critical role in global warming and the global carbon cycle via the production of methane.
== Cold Adaptation ==
''M. burtonii'' are thermally regulated, thus highlighting the role that energy generation and biosynthesis pathways play in cold adaptation. proteomic research shows that cellular levels of subunit E are higher during growth at low temperatures.〔 This could possibly indicate that Subunit E is fulfilling a specific role in regulating the transcription of genes involved in low temperature growth or in facilitating transcription at low temperature in general.〔 ''M. burtonii'' have regulatory mechanisms resembling those found in cold shock induced RNA helicase genes from ''E. coli''. Thus, these mechanisms have similarity with bacterial methods of cold adaptation.〔 ''M. burtonii'' have decreased levels of DnaK and increased levels of PPIase at 4 degrees Celsius possibly indicating the protein folding is a thermally sensitive process and may contribute to its adaptation to the cold.〔 A number of genes involved in methanogenesis are thermally regulated, and regulation involves the expression of genes in operons, protein modification, and the synthesis of Pyrrolysine containing TMA-MT.〔 At 4 °C higher levels of protein and/or mRNA are expressed for genes involved in methanogenesis which produces a proton motive force that drives cellular processes including ATP synthesis, and pathways from acetyl-CoA leading to amino acid metabolism.〔 ''M. burtonii'' have increased levels of GDH and GAPDH (key enzymes in nitrogen and carbon metabolism) at 4 °C indicating that there is an effective regulation of fundamental processes of carbon and nitrogen metabolism consistent with the evolution of the organism for growth in the cold.〔
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