Acidilobus saccharovorans

Acidilobus saccharovorans is a thermoacidophilic (that is, both thermophilic and acidophilic) species of anaerobic archaea. The species was originally described in 2009 after being isolated from hot springs in Kamchatka.[2][3]

Acidilobus saccharovorans
Scientific classification
Domain:
Archaea
Phylum:
Thermoproteota
Class:
Thermoprotei
Order:
Acidilobales
Family:
Acidilobaceae
Genus:
Acidilobus
Species:
A. saccharovorans
Binomial name
Acidilobus saccharovorans
Prokofeva et al., 2009[1][2]

Description

A. saccharovorans has a coccoid morphology of 1–2 μm diameter with a relatively thick S-layer and a bundle of flagella. It has an optimal growth temperature of 80–85°C (qualifying it as a hyperthermophile) and an optimal pH of 3.5–4.0. It is an obligate anaerobe with fermentative metabolism. Its growth is accelerated by the presence of elemental sulfur, which is reduced to hydrogen sulfide; however, sulfur is not essential for growth. It is resistant to the antibiotics chloramphenicol, penicillin and streptomycin.[2] A. saccharovorans differs from A. aceticus, the only other recognized species in the genus, in two major respects: it is flagellated whereas A. aceticus is non-motile; and it is capable of growth on a wider variety of substrates, including many sugars and polysaccharides.[4][3] Its name refers to this property of its metabolism.[2]

Genome and metabolism

The A. saccharovorans genome sequence was reported in 2010 as the first full genome of an archaeon that is thermoacidophilic and obligately anaerobic.[5] The genome contains genes consistent with the Embden-Meyerhof and Entner-Doudoroff metabolic pathways. Unexpectedly, it was also found to contain genes encoding the oxidative tricarboxylic acid cycle enzymes, albeit without the key enzyme, ATP citrate lyase, that would enable the pathway to operate reductively. Unusually for an archaeon, it encodes a beta-oxidation pathway, which would be expected to enable it to grow on triacylglycerides and fatty acids.[5] However, these metabolic capacities have not yet been demonstrated experimentally.[6] The predicted proteome also contains a number of features interpreted as adaptation to growth in acidic conditions by making use of the high extracellular concentration of protons.[5]

Phylogenetics

Comparison to other sequenced genomes suggests that A. saccharovorans is most closely related to Aeropyrum pernix. The genome also contains evidence of horizontal gene transfer between Acidilobales and Sulfolobales, an order of aerobic thermoacidophiles often found in the same hot springs. The A. saccharovorans genome sequence was originally reported to support establishment of a new order, Acidilobales, containing the families Acidilobaceae and Caldisphaeraceae,[5] which is currently accepted.[1] However, a 2015 phylogenomics study of conserved archaeal protein sequences suggested that the two families instead were better placed in the order Desulfurococcales, which also contains Aeropyrum pernix.[7]

Ecology

Acidilobales species are widely distributed in hot springs with acidic environments, where they likely play a role in the complete oxidation of organic material. Based on the metabolic capacities predicted from the A. saccharovorans genome, Acidilobales are metabolically similar to the Thermoproteales, and the two orders may serve similar ecological roles in acidic and neutral hot springs, respectively.[2][6]

References
  1. "Acidilobus aceticus". Integrated Taxonomic Information System. Retrieved 10 June 2016.
  2. Prokofeva, MI; Kostrikina, NA; Kolganova, TV; Tourova, TP; Lysenko, AM; Lebedinsky, AV; Bonch-Osmolovskaya, EA (December 2009). "Isolation of the anaerobic thermoacidophilic crenarchaeote Acidilobus saccharovorans sp. nov. and proposal of Acidilobales ord. nov., including Acidilobaceae fam. nov. and Caldisphaeraceae fam. nov". International Journal of Systematic and Evolutionary Microbiology. 59 (Pt 12): 3116–22. doi:10.1099/ijs.0.010355-0. PMID 19643887.
  3. Prokofeva, Maria; Merkel, Alexander; Lebedinsky, Alexander; Bonch-Osmolovskaya, Elisaveta (2014). "The Family Acidilobaceae". The Prokaryotes: Other Major Lineages of Bacteria and the Archaea: 9–14. doi:10.1007/978-3-642-38954-2_332. ISBN 978-3-642-38953-5.
  4. Prokofeva, MI; Miroshnichenko, ML; Kostrikina, NA; Chernyh, NA; Kuznetsov, BB; Tourova, TP; Bonch-Osmolovskaya, EA (November 2000). "Acidilobus aceticus gen. nov., sp. nov., a novel anaerobic thermoacidophilic archaeon from continental hot vents in Kamchatka". International Journal of Systematic and Evolutionary Microbiology. 50 (6): 2001–8. doi:10.1099/00207713-50-6-2001. PMID 11155973.
  5. Mardanov, AV; Svetlitchnyi, VA; Beletsky, AV; Prokofeva, MI; Bonch-Osmolovskaya, EA; Ravin, NV; Skryabin, KG (August 2010). "The genome sequence of the crenarchaeon Acidilobus saccharovorans supports a new order, Acidilobales, and suggests an important ecological role in terrestrial acidic hot springs". Applied and Environmental Microbiology. 76 (16): 5652–7. Bibcode:2010ApEnM..76.5652M. doi:10.1128/aem.00599-10. PMC 2918975. PMID 20581186.
  6. Bonch-Osmolovskaya, Elisaveta (2012). "Metabolic diversity of thermophilic prokaryotes—what's new.". Extremophiles: microbiology and biotechnology. Norfolk: Caister Academic Press. pp. 109–31. ISBN 9781904455981.
  7. Petitjean, C; Deschamps, P; López-García, P; Moreira, D; Brochier-Armanet, C (May 2015). "Extending the conserved phylogenetic core of archaea disentangles the evolution of the third domain of life". Molecular Biology and Evolution. 32 (5): 1242–54. doi:10.1093/molbev/msv015. PMID 25660375.
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