Thermoproteous tenax

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Image of thinly sliced Thermoproteus tenax cells in the process of dividing. Image credit: Wildhaber and Baumeister 1987.

Classification

Archaea; Thermoproteota; Thermoprotei; Thermoproteales; Thermoproteaceae

Species

NCBI: [1]

Thermoproteus tenax

Description and Significance

Thermoproteus tenax is a hyperthermophilic archaeal organism first discovered in volcanic fields in Iceland, known as solfataras (Zillig et al., 1981). It is a strict anaerobe that is notable for its ability to grow both chemolithoautotrophically and chemoorganoheterotrophically (Siebers et al., 2011). It is dependent on sulfur for growth, which functions as its final electron receptor (Siebers et al., 2011).

Thermoproteus tenax is rod shaped with variable length and encompassed by a protein S-layer with a hexagonal lattice structure (Wildhaber and Baumeister, 1987). It is unique in that it is the first member of the Thermoproteus genus to have a fully sequenced genome (Siebers et al., 2011).

Genome Structure

The genome of Thermoproteus tenax is 1,841,542 base pairs long and contains 91 unique open reading frames (Siebers et al., 2011). The single circular chromosome contains 2,051 protein-encoding open reading frames with an average length of 813 base pairs and a predicted 1,552 assigned functions (Siebers et al., 2011). It has an average GC content of 55.13%, which is higher than average for the archaea domain (Siebers et al., 2011; Li and Du, 2014). For each of the genes encoding for ribosomal RNA (23S, 16S, and 5S), only one copy is present in the genome (Siebers et al., 2011).

Cell Structure, Metabolism and Life Cycle

Thermoproteus tenax are nonmotile, rod-shaped microbes that are gram-negative staining (Messner et al., 1986). As mentioned prior, the exterior S-layer is hexagonal in its lattice structure, which is thought to contribute to the maintenance of shape and high resistance to extreme temperatures, acidity, and mechanical disturbances (Messner et al., 1986).

In the presence of hydrogen and carbon dioxide, Thermoproteus tenax has the ability to grow chemolithoautotrophically and gains energy using hydrogen oxidation. (Siebers et al., 2011) The electron transport chain is short and simplified, with sulfur acting as the final electron acceptor. (Siebers et al., 2011).

Under chemoorganoheterotrophic growth, a modified glycolysis pathway is followed by the citric acid cycle, where organic compounds such as sugars, organic acids, and alcohols, are oxidized (Siebers et al., 2011). The electron transport chain (a separate one than mentioned before) is located in the cellular membrane and also utilizes sulfur as the final electron receptor (Siebers et al., 2011).

In addition, Thermoproteus tenax was found to have an ATP synthase that is standard for most archaea, termed

A₀A₁-ATP Synthase.

A diagram of the metabolic pathways of Thermoproteus tenax . Image credit: Siebers et al., 2011

Ecology and Pathogenesis

No archaea described in literature thus far have been identified as pathogenic (Moissl-Eichinger et al., 2017).

As mentioned previously, Thermoproteus tenax is hyperthermophilic, growing at an optimum temperature of 86 degrees Celsius in slightly acidic conditions (Siebers et al., 2011; Messner et al., 1986). While no literature has described the possible environmental associations of this microbe, members of a sister genus, Pyrobacula , are thought to contribute to mineral formation within sediments of geothermal environments (Stewart et al., 2018). These Pyrobacula have been experimentally shown to contribute to the green coloration of the sediments, which act as substrates for the archaea to perform iron-reducing activity (Stewart et al., 2018).

References

Li, X.Q., Du, D. (2014) Variation, Evolution, and Correlation Analysis of C+G Content and Genome or Chromosome Size in Different Kingdoms and Phyla. PLoS One 9: e88339. doi:10.1371/journal.pone.0088339

Messner, P., Sara, M., Stetter, K.O., Sleytr, U.B. (1986) “Ultrastructure of the Cell Envelope of the Archaebacteria Thermoproteus tenax and Thermoproteus neutrophilus”. Journal of Bacteriology 166: 1046-1054. doi: https://doi.org/10.1128/jb.166.3.1046-1054.1986

Moissl-Eichinger, C., Pausan, M., Taffner, M., Taffner, J., Berg, G., Bang, C., Schmitz, A. (2017) Archaea Are Interactive Components of Complex Microbiomes. Trends in Microbiology 26:70-85. doi: https://doi.org/10.1016/j.tim.2017.07.004

Siebers, B., Zaparty, M., Raddatz, G., Tjaden, B., Albers, SV., Bell, S., Blombach, F., Kletzin, A., Kyrpides, N., Lanz, C., Plagens, A., Rampp, M., Rosinus, A., Jan, M., Makarova, K.S., Klenk, HP., Schuster, S.C., Hensel, R. (2011) “The Complete Genome Sequence of Thermoproteus tenax: A Physiologically Versatile Member of the Crenarchaeota”. PLoS One 6:e24222. doi: 10.1371/journal.pone.0024222.

Stewart, L.C., Houghton, K., Carere, C.R., Power, J.F., Chambefort, I., Stott, M.B. (2018) Interaction between ferruginous clay sediment and an iron-reducing hyperthermophilic Pyrobaculum sp. in a terrestrial hot spring. FEMS Microbiology Ecology 94:33-11. doi: https://doi.org/10.1093/femsec/fiy160

Wildhaber I., Baumeister W. (1987) “The cell envelope of Thermoproteus tenax: three-dimensional structure of the surface layer and its role in shape maintenance”. The EMBO Journal 6:1475-80. doi: 10.1002/j.1460-2075.1987.tb02389.x.

Zillig, W., Stetter, K.O., Schäfer, W., Janekovic, D., Wunderl, S., Holz, I., Palm, P. (1981) “Thermoproteales: A novel type of extremely thermoacidophilic anaerobic archaebacteria isolated from Icelandic solfataras”. Zentralblatt für Bakteriologie Mikrobiologie und Hygiene: I. Abt. Originale C: Allgemeine, angewandte und ökologische Mikrobiologie 2:205-227. https://doi.org/10.1016/S0721-9571(81)80001-4

Author

Page authored by Audrey Groves, student of Prof. Bradley Tolar at UNC Wilmington.