Thermoplasmatales

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Thermoplasmatales
Systematics
Domain : Archaea (Archaea)
Department : Euryarchaeota
Class : Thermoplasmata
Order : Thermoplasmatales
Scientific name
Thermoplasmatales
Brock 1970

The Thermoplasmatales are the only order of the Thermoplasmata class within the Archaea . They include three families with four genera of thermophilic and extremely acidophilic , i.e. heat and acid-loving microorganisms. Their optimum growth is 40 to 60 ° C and a pH value of 0.5 to 2. They are the only known living beings that can survive and grow at a pH value below 0. The pH value inside the cell is kept constant at around 7. Thermoplasmatales are spherical, only 0.5 to 2 µm large archaea without a cell wall . Some species have flagella . They likely feed on the organic remains of other living things that have perished from the extreme environmental conditions of their habitat.

Systematics

The order consists of four genera in three families:

  • Family Ferroplasmaceae Golyshina et al. 2000
    • Genus Ferroplasma Golyshina et al. 2000
  • Family Picrophilaceae Schleper et al. 1996
    • Genus Picrophilus Schleper et al. 1996
  • Thermoplasmataceae Reysenbach family 2002
    • Genus Thermoplasma Darland et al. 1970
  • incertae sedis

Thermoplasm

Thermoplasma acidophilum and T. volcanium grow optimally at a temperature of 55 to 60 ° C and a pH value of around 2. They can breathe sulfur anaerobically or grow aerobically. They were described for the first time by TD Brock in 1970. Due to the lack of a cell wall, they were assigned to the mycoplasmas at that time . They can be found, for example, on self-igniting coal spoil heaps, as they can utilize the coal residues created there by combustion. T. volcanium is also found on volcanic, acidic soils. The cell membrane consists of lipoglycan . The backbone of this molecule consists of tetraether lipid monolayers. Sugar molecules like mannose and glucose are linked to the ether lipids . In addition, glycoproteins are embedded in the membrane , which leads to greater stability at high temperatures. The genome is relatively small at 1.56 Mbp. 1509 open reading frames could be located on it. The DNA is packaged into spherical structures using basic proteins.

Ferroplasma

Ferroplasma is not thermophilic, so it grows at lower temperatures around 35 ° C. Ferroplasma has the ability to oxidize iron (Fe2 + to Fe3 +). Since this reaction produces acid, this acidophilic organism creates an optimal environment for itself. Iron is not only used to generate energy, it also plays a role in anabolism . It was found that more than 80 percent of the proteins in Ferroplasma acidiphilum contain iron atoms. Find one can Ferro plasma especially in acidic mine water.

Picrophilus

Picrophilus has a cell wall made up of protein. In contrast to ferroplasma and thermoplasma, its GC content is low. Picrophilus is arguably the most acid-tolerant organism in the world. Its growth optimum is at pH 0.7. However, it can also grow to pH −0.06. The reason for this extreme acidophilicity is probably the lipid arrangement of the cell membrane. In an extremely acidic environment, the lipids lie close together. At a higher pH value (from pH4), however, gaps arise between the lipids, which ultimately leads to the degradation of the membrane.

literature

  • G. Darland, TD Brock, W. Samsonoff, SF Conti: A thermophilic acidophilic mycoplasm isolated from a coal refuse pile. In: Science. 170, 1970, pp. 1416-1418.
  • TD Brock: Thermophilic microorganisms and life at high temperatures. Springer, Berlin / Heidelberg / New York 1978, ISBN 3-540-90309-7 , pp. 92-116.
  • A. Segerer, KO Stetter: The Genus Thermoplasma. In: A. Balows, HG Trüper, M. Dworkin, W. Harder, KH Schleifer (eds.): The Prokaryotes. Springer, New York 1992, pp. 712-718.
  • A. Segerer, TA Langworthy, KO Stetter: Thermoplasma acidophilum and Thermoplasma volcanium sp. nov. from Solfatara Fields. In: Syst. Appl. Microbiol. 10, 1988, pp. 161-171.
  • Michael T. Madigan, John M. Martinko (Eds.): Brock Microbiology. 11th edition. Pearson Studies, Munich / Boston 2006, ISBN 3-8273-7187-2 .

Individual evidence

  1. a b C. Schleper, G. Puehler, I. Holz, A. Gambacorta, D. Janekovic, U. Santarius, HP Klenk, W. Zillig: Picrophilus gen. Nov., Fam. nov .: a Novel Aerobic, Heterotrophic, Thermoacidophilic Genus and Family Comprising Archaea Capable of Growth around pH 0. In: J Bacteriol. 177 (24), Dec 1995, pp. 7050-7059.
  2. Joel Cracraft, Michael J. Donoghue: Assembling the tree of life . Oxford University Press US, 2004, ISBN 0-19-517234-5 , pp. 58-59 .