Thermotogales

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Thermotogales
Systematics
Classification : Creature
Domain : Bacteria (bacteria)
Department : Thermotogae
Class : Thermotogae
Order : Thermotogales
Scientific name
Thermotogales
Reysenbach 2002 emend. Bhandari & Gupta 2014

The Thermotogales are an order of bacteria within the Thermotogae class . It is a phylogenetically old group of bacteria. The species are of particular interest to biotechnology due to the formation of thermostable proteins and enzymes as well as the production of molecular hydrogen (H 2 ) .

features

Appearance

The so-called toga are conspicuous , they are bubble-shaped protuberances of protein shells at both ends of the cell. This structure gave it its name. The toga corresponds to the outer cell membrane of gram-negative bacteria, the periplasm is located between the toga and the inner membrane. In the species Fervidobacterium islandicum , the protuberance is only formed at one end of the cell. This outer shell is very different from the outer membrane of the Proteobacteria . In contrast to the Proteobacteria, the Thermotogae lack lipopolysaccharides (LPS), and the outer membrane is mainly made up of proteins. Ompα and Ompβ proteins are important here. The latter form a hexagonal grid. Ompα binds the toga to the inner cell bodies. In the species T. maritima , further enzymes were found that are associated with the transport of substances and signal transmission.

As with the Proteobacteria, there is a peptidoglycan layer between the two membranes . In contrast to those of the Proteobacteria, the peptidoglycans of Thermotogales do not contain meso-diaminopimelic acid (DAP), but D- lysine and L-lysine.

Two examples of membrane lipids at Thermotogales. a) a dicarboxylic acid (a fatty acid with 32 carbon atoms (15,16-dimethyltriacontanedioic acid, C 32 H 62 O 4 ), b) an ether lipid made from 2 dicarboxylic acids with a total of 70 carbon atoms. Please click to enlarge.

Another characteristic of the Thermotogales is the presence of long-chain fatty acids and dicarboxylic acids in the membrane lipids. Examples of the dicarboxylic acids are chains of 30, 32 or 34 carbon atoms with two carboxylic acid groups . They are likely used for stability in extremely high temperature environments. C 16: 0 fatty acids ( palmitic acid ) are also common within the membranes of the species of the order. Bipolar tetraethers were also found in the species Thermotoga maritima . These are 2 dicarboxylic acids that are bound to two glycerine molecules with ether bonds (see picture).

Structural formula of isoprene, basic building block of lipids in archaea

The lipids, which consist of long-chain fatty acids, are similar to the membrane lipids of archaea . In this group, the membrane consists of polyisoprene chains that are linked to glycerol molecules by ether bonds. The basic building block here is the alkene isoprene . The differences are the missing double bonds and the few branches of the lipids in the Thermotogae.

In the mesophilic species "Mesotoga prima" there are no long-chain lipids with over 30 carbon atoms. This bacterium shows optimal growth at a temperature of 37 ° C, at over 50 ° C no further growth takes place.

The Gram staining of Thermotogales is gram- negative, despite the differences to the Proteobacteria.

Most types of Thermotogales have flagella and are motile. The flagella can be designed differently depending on the species, so Thermotoga maritima has a single flagella, which is located near one end of the cell (subpolar). Pseudothermotoga elfii is flagellated peritrich, many flagella are evenly distributed over the surface. Thermotoga neapolitana has no flagella. Thermosipho is also not flagellated.

The mostly rod-shaped cells can occur individually, in pairs or in chains, depending on the type. In Fervidobacterium riparium, chains of up to 17 individual cells can occur. Fervidobacterium islandicum can form aggregates of up to 50 cells. Spores are not formed.

metabolism

The individual representatives of the order live in areas where there is no oxygen, they are anaerobic . They use the fermentation ( fermentation ) to produce energy. You can ferment a number of substrates, including complex organic substances such as yeast extract or starch. Carbohydrates such as glucose and xylose can also be used. For example, types of Thermotogales produce lactic acid (lactate), acetate , carbon dioxide and hydrogen (H 2 ) as fermentation products during fermentation to generate energy . Elemental sulfur or thiosulfate , for example, can also be used as electron acceptors by the various species. This happens when there is too much of the growth inhibiting hydrogen (H 2 ) in the medium. Thermotoga can also perform anaerobic respiration with hydrogen as the electron donor and iron (III) ions as the electron acceptor.

Genetic studies of Thermotoga maritima have shown a variety of metabolic pathways. The bacterium uses the Entner-Doudoroff path and glycolysis as well as the non-oxidative part of the pentose phosphate path . This diversity is also reflected in the fact that about 7% of the genome of Thermotoga maritima are required for glucose metabolism. Large parts of the genome that are involved in metabolism have also been identified in other members of the Thermotogales order.

The salt tolerance of Thermotoga species varies widely, some showing high salt tolerance ( halophilia ), while others are restricted to habitats with a low salt content.

genetics

The genome of Thermotoga maritima has been completely sequenced . It was found that there is a strong similarity to heat-loving (thermophilic) archaea . It is assumed that more than 20% of the genes were transferred from archaea to Thermotoga maritima by horizontal gene transfer. Archaea genes have also been found in other representatives of bacteria , such as Aquifex aeolicus , but Thermotoga is the largest known horizontal gene transfer between the two main groups of prokaryotes, the archaea and bacteria. The transfer took place well after the phylogenetic separation of the two large groups.

Systematics

The Thermotogales order was drawn up in 2002 by Anna-Louise Reysenbach . It consists of two families with two genera each (as of June 2020). The order belongs to the Thermotogae class and the department of the same name . The type genus is Thermotoga . In the class of Thermotogae there are four orders: The Kosmotogales , Mesoaciditogales , Petrotogales and the Thermotogales.

After the establishment of the Thermotogales order in 2004, only one family, the Thermotogaceae, was initially assigned to the order. The Thermotogales were also the only order of the Thermotogae department. At that time, the genera Fervidobacterium , Thermosipho , Geotoga and Petrotoga belonged to this family. In the further course, further phylogically related species were newly described. Further investigation of the 16S rRNA led to the proposed extension of the class Thermotogae in 2013. Two additional orders were introduced, the Kosmotogales and the Petrotogales. In 2016 the order Mesoaciditogales was also introduced.

The following is a list of the families and genera of the Thermotogales order:

  • Fervidobacteriaceae Bhandari and Gupta 2014
    • Fervidobacterium Patel et al. 1985
    • Thermosipho Huber et al. 1989
  • Thermotogaceae
    • Pseudothermotoga Bhandari and Gupta 2014
    • Thermotoga Stetter and Huber 1986

ecology

The types of Thermotogales come in habitats with high temperatures, such as B. in oil deposits, hot freshwater springs or in hot deep sea springs of the sea ( geothermal deep sea springs ). Such bacteria are known as thermophilic ("heat-loving"). Many species also require a high salt content, they are halophilic ("salt-loving"). The species Fervidobacterium nodosum occurs in volcanic areas where sulfur escapes (so-called solfataras ).

A table with details of the tolerated temperature ranges and the temperature for optimal growth of some types of Thermotogales. Please click to enlarge.

Thermotoga maritima is the first species of the Bacteria domain to be discovered that tolerates temperatures above 80 ° C. One speaks here of hyperthermophilic bacteria. The bacterium was first described in 1986 by a team led by Robert Huber . This ability to grow at temperatures above 80 ° C was previously only known from the archaea. Currently (2017) hyperthermophilic microorganisms in Bacteria are only in the strains Thermotogae , Thermodesulfobacteria and Aquificae known.

Use by humans

The various heat-resistant proteins and enzymes of the thermophilic species are of interest to biotechnology. Thermotoga maritima was examined in particular . Areas of application are, for example, detergents that are used at high temperatures. Here, enzymes are used to split the peptides. Another example is also available from Thermotoga maritima native Tma polymerase used for the polymerase chain reaction ( polymerase chain reaction is used PCR). It is a special thermostable DNA polymerase that is used to copy DNA sections. Another application example is bleaching in papermaking. For this purpose, enzymes, so-called xylanases , were examined by Thermotoga maritima . Many types of Thermotogae form hydrogen gas (H 2 ), which is of interest for the biological production of alternative fuels.

Individual evidence

  1. ↑ James W. Brown: Principles of Microbial Diversity . Wiley, 2014. ISBN 9781555814427
  2. ↑ a b Jaap S. Sinninghe Damsté, W. Irene C. Rijpstra, Ellen C. Hopmans, Stefan Schouten, Melike Balk and Alfons JM Stams: Structural characterization of diabolic acid-based tetraester, tetraether and mixed ether / ester, membrane-spanning lipids of bacteria from the order Thermotogales In: Archives of Microbiology (2007) 188: pp. 629-641. doi : 10.1007 / s00203-007-0284-z
  3. ↑ a b c d e Eugene Rosenberg, Edward F. DeLong, Stephen Lory, Erko Stackebrandt and Fabiano Thompson: The Prokaryotes. Other Major Lineages of Bacteria and The Archaea . Springer, 2014. ISBN 978-3-642-38955-9
  4. ↑ Camilla L. Nesbø, Danielle M. Bradnan, Abigail Adebusuyi, Marlena Dlutek, Amanda K. Petrus, Julia Foght, W. Ford Doolittle & Kenneth M. Noll: Mesotoga primagen. nov., sp. nov., the first described mesophilicspecies of the Thermotogales In: Extremophiles (2012) 16: pp. 387 - 393. doi : 10.1007 / s00792-012-0437-0
  5. ↑ a b c d George M. Garrity (Ed.): The Archaea and the deeply branching and phototrophic Bacteria. Springer, New York 2001, ISBN 0-387-98771-1
  6. ↑ Olga A. Podosokorskaya, Alexandr Yu. Merkel, Tatyana V. Kolganova, Nikolai A. Chernyh, Margarita L. Miroshnichenko, Elizaveta A. Bonch-Osmolovskaya and Ilya V. Kublanov: Fervidobacterium riparium sp. nov., a thermophilicanaerobic cellulolytic bacterium isolated from a hotspring In: International Journal of Systematic and Evolutionary Microbiology (2011), 61, pp. 2697-2701. doi : 10.1099 / ijs.0.026070-0
  7. ↑ a b Michael T. Madigan, John M. Martinko, David A. Stahl and David P. Clark: Brock Mikrobiologie . Pearson Studies, 2013. ISBN 9783868941449
  8. ^ A b Joan L. Slonczewski, John W. Foster, Birgit Jarosch, Lothar Seidler, Olaf Werner and Jessica Hilbig: Microbiology: A Science with a Future Spectrum Academic Publishing, 2012. ISBN 9783827429094
  9. ↑ Systematics according to JP Euzéby: List of Prokaryotic names with Standing in Nomenclature (LPSN) (as of June 19, 2020)
  10. ↑ Vaibhav Bhandari and Radhey S. Gupta: Molecular signatures for the phylum (class) Thermotogae and a proposal for its division into three orders (Thermotogales, Kosmotogales ord. Nov. And Petrotogales ord. Nov.) Containing four families (Thermotogaceae, Fervidobacteriaceae fam nov., Kosmotogaceae fam. nov. and Petrotogaceae fam. nov.) and a new genus Pseudothermotoga gen. nov. with five new combinations. In: Antonie van Leeuwenhoek (2014), 105, pp. 143-168 doi : 10.1007 / s10482-013-0062-7
  11. ^ Rolf D. Schmid: Pocket Atlas of Biotechnology and Genetic Engineering . ISBN 978-3-527-33514-5

literature

Web links