Haloferax volcanii

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Haloferax volcanii
Haloferax volcanii

Haloferax volcanii

Systematics
Department : Euryarchaeota
Class : Halobacteria
Order : Haloferacales
Family : Haloferacaceae
Genre : Haloferax
Type : Haloferax volcanii
Scientific name
Haloferax volcanii
( Mullakhanbhai & Larsen 1975) Torreblanca et al. 1986

Haloferax volcanii is a species of the genus Haloferax , which belongs to the archaea ( Archaea ).

description

The microbiologist Benjamin Elazari Volcani discovered Haloferax volcanii for the first time in the 1930s , an extremophilic organism named after him. H. volcanii is a halophilic mesophilic archaeon that can be isolated from hypersaline environments such as the Dead Sea, Great Salt Lake, and oceanic environments with high concentrations of sodium chloride. Haloferax volcanii is notable because it can be cultivated without much difficulty, which is rare in an extremophile.

H. volcanii is chemoorganotrophic and metabolizes sugar as a carbon source. It is primarily aerobic but can perform anaerobic breathing under anoxic conditions.

Cell structure and metabolism

Reproduction under H. volcanii occurs asexually through binary fission. This practice is similar with other archaea and also with bacteria. H. volcanii cells do not have a cell wall and therefore, like many archaea, use their outer S-layer as a structure. A single H. volcanii archaeon, i.e. a cell, can vary from 1–3 micrometers in diameter. They are typically pleiomorphic, so they can be seen in other forms, including coccoid.

Haloferax volcanii was grown under laboratory conditions and imaged with a phase contrast microscope. The cells were attached to an agar pad.

The membranes of this organism consist of the typical ether-bound membrane lipids that are only found in archaea and also contain a high proportion of carotenoids including lycopene, which gives them their characteristic red color. H. volcanii uses a method to maintain osmostasis in which salt is used rather than the corresponding, typical method observed in bacteria. This method maintains a high level of potassium ions in the cell to balance the sodium ions outdoors.

For this reason, H. volcanii has a complex ion regulation system and is chemoautotrophic. H. volcanii grows optimally at 42 ° C with an NaCl concentration of 1.5–2.5  M in a complex nutrient medium; It also grows at 37 ° C but still requires the concentrated NaCl and complex medium. Because of the salt in this method, cytoplasmic proteins are structured so that they are properly folded in the presence of high ionic concentrations. To do this, they typically have a large number of charged residues on the outer portion of the protein and very hydrophobic residues that form a core. This structure increases its stability in saline solution and even in high temperature environments considerably, but results in some loss of processivity compared to bacterial homologues.

The only source of ATP for H. volcanii is breathing. In contrast to other Halobacteriacae, such as B. Halobacterium salinarum , unable to operate photophosphorylation because the bacteriorhodopsin required for it is missing.

ecology

Isolates of volcanii H. are commonly found in sea salt rich waters such as the Dead. Their exact role in the ecosystem is uncertain, but the carbohydrates found in these organisms may serve many practical purposes. Because of its ability to maintain homeostasis despite the salt around it, H. volcanii could become important for biotechnological advancement. H. volcanii and comparable species also provide interesting information about genetics and evolution, as they differ in essential points from many other organisms. This concerns z. B. the type and extent of replication and recombination.

Dead Sea

The Dead Sea contains a very high concentration of sodium, magnesium and calcium salts. This combination makes the sea an ideal environment for extremophiles like H. volcanii . The Dead Sea has a diverse community of microorganisms, with Kaplan and Friedman's field tests showing that H. volcanii had the greatest numerical presence within the community. It is common for higher numbers of the halophile to occur during the summer as the Dead Sea is much warmer, averaging 37 ° C , making it  more suitable for bacterial blooms. The Dead Sea is likely to become less hospitable even to the extremophiles who live there, as the salinity increases. This is attributed to both natural factors and human activities, and it also affects the species Haloferax volcanii , for which changes in salinity in their predominant environment are a risk.

Genome structure

The H. volcanii genome consists of a large (4 Mbp ), multiscopic chromosome and several megaplasmids. The full genome, DS2, of H. volcanii consists of approximately 4130 genes. The genome has been fully sequenced and an article about it was published in 2010. H. volcanii molecular biology has been studied extensively over the past decade to learn more about DNA replication, DNA repair, and RNA synthesis. The archaeal proteins used in these processes are extremely similar to eukaryotic proteins and are therefore the preferred model systems for these organisms. H. volcanii is subject to a mechanism of "pairing" and cell fusion, which leads to extensive horizontal gene transfer.

DNA damage and repair

In prokaryotes, the DNA genome is organized in a dynamic structure, the nucleoid, in which it is embedded in the cytoplasm. Exposure of Haloferax volcanii to stresses that damage DNA leads to the densification and reorganization of the nucleoid.

The compaction depends on the Mre11-Rad50 protein complex, which is used in the homologous recombination repair of DNA double-strand breaks. Delmas et al. Suggested that nucleoid densification could be part of a DNA damage response that accelerates cell healing by helping DNA repair proteins locate targets and making it easier to find intact DNA sequences during homologous recombination.

Genetic exchange

H. volcanii cells can undergo a paired genetic exchange that involves cell fusion that results in a heterodiploid cell (containing two different chromosomes in one cell).

Cells of a related species, Haloferax mediterranei , can also exchange genetically with one another. H. volcanii has an average nucleotide sequence match with H. mediterranei of 86.6%. At a reduced frequency, cells of these two species can also interact to undergo genetic exchange. During this process, a diploid cell is formed that contains the full genetic repertoire of both parental cells, and genetic recombination is facilitated. The cells then separate, creating recombinant cells.

Astrobiology

The conditions under which Haloferax volcanii survived, high salinity and high radiation, are very similar to the conditions on the surface of Mars. Consequently, the organism is currently being used to test the survivability of earthborn extremophiles on Mars. Advances in this area could lead to a better understanding of the possibilities and timeline of extraterrestrial life.

See also

further reading

  • M. Cerletti, MJ Martínez, MI Giménez, DE Sastre, RA Paggi, RE De Castro: The LonB protease controls membrane lipids composition and is essential for viability in the extremophilic haloarchaeon Haloferax volcani. In: Environmental microbiology. Volume 16, Number 6, June 2014, pp. 1779–1792, doi : 10.1111 / 1462-2920.12385 , PMID 24428705 .
  • S. Chimileski, MJ Franklin, RT Papke: Biofilms formed by the archaeon Haloferax volcanii exhibit cellular differentiation and social motility, and facilitate horizontal gene transfer. In: BMC Biology. Volume 12, 2014, doi : 10.1186 / s12915-014-0065-5 .
  • NE Gibbons: Family V. Halobacteriaceae fam. nov. In Bergey's Manual of Determinative Bacteriology . Ed .: RE Buchanan & NE Gibbons. 8th edition. The Williams & Wilkins Co, Baltimore 1974, ISBN 0-683-01117-0 .
  • A. Oren, A. Ventosa: International Committee on Systematic Bacteriology Subcommittee on the Taxonomy of Halobacteriaceae. Minutes of the meetings, August 16, 1999, Sydney, Australia. In: International journal of systematic and evolutionary microbiology. Volume 50 Pt 3, May 2000, pp. 1405-1407, doi : 10.1099 / 00207713-50-3-1405 , PMID 10843089 .
  • J. Parente, A. Casabuono, MC Ferrari, RA Paggi, RE De Castro, AS Couto, MI Giménez: A rhomboid protease gene deletion affects a novel oligosaccharide N-linked to the S-layer glycoprotein of Haloferax volcanii. In: Journal of Biological Chemistry . Volume 289, number 16, April 2014, pp. 11304-11317, doi : 10.1074 / jbc.M113.546531 , PMID 24596091 , PMC 4036268 (free full text).
  • M. Torreblanca, F. Rodriguez-Valera, G. Juez, A. Ventosa, M. Kamekura, M. Kates: Classification of Non-alkaliphilic Halobacteria Based on Numerical Taxonomy and Polar Lipid Composition, and Description of Haloarcula gen. Nov. and Haloferax gen. nov .. In: Systematic and Applied Microbiology. 8, 1986, p. 89, doi : 10.1016 / s0723-2020 (86) 80155-2 .

Individual evidence

  1. ↑ A. Oren: The Order Halobacteriales. In The Prokaryotes: A Handbook on the Biology of Bacteria . 3. Edition. Springer, New York 2006, p. 113-164 .
  2. ↑ A. Zaigler, SC Schuster, J. Soppa: Construction and usage of a onefold-coverage shotgun DNA microarray to characterize the metabolism of the archaeon Haloferax volcanii . In: Molecular microbiology. Volume 48, Number 4, May 2003, pp. 1089-1105, PMID 12753198 .
  3. ↑ GM Garrity, RW Castenholz, DR Boone: The Archaea and the Deeply Branching and Phototrophic Bacteria . 2nd Edition. Springer, New York 2001, p. 316 .
  4. ↑ H. volcanii is a chemoorganotroph requiring complex nutrient medium and 1.5-2.5 M NaCl for growth. Cultures will grow at 37C, but optimal growth is at 42C. , archaea.ucsc.edu - haloVolc1 , accessed 2018-08-31.
  5. ↑ D. Ausiannikava, L. Mitchell, H. Marriott, V. Smith, M. Hawkins, KS Makarova, EV Koonin, CA Nieduszynski, T. Allers: Evolution of Genome Architecture in Archaea: Spontaneous Generation of a New Chromosome in Haloferax volcanii . In: Molecular biology and evolution. Volume 35, number 8, August 2018, pp. 1855–1868, doi : 10.1093 / molbev / msy075 , PMID 29668953 , PMC 6063281 (free full text).
  6. ↑ A. Orlen: Population dynamics of halobacteria in the Dead Sea water column. "Limnology and Oceanography . In: Limnology and Oceanography . Volume 28 , no. 6 , 1983, pp. 1094-1103 .
  7. ↑ MF Mullakhanbhai, H. Larsen: spec Halobacterium volcanii. nov., a Dead Sea halobacterium with a moderate salt requirement. In: Archives of microbiology. Volume 104, Number 3, August 1975, pp. 207-214, PMID 1190944 .
  8. ↑ D. Neev, KO Emery: The Dead sea, depositional processes and environments of Evaporites . In: Geol. Surv. Bull. State of Israel 1967.
  9. ↑ UCSC Genome Browser Gateway , archaea.ucsc.edu, 2017-04-20
  10. Jump up ↑ AL Hartman, C. Norais, JH Badger, S. Delmas, S. Haldenby, R. Madupu, J. Robinson, H. Khouri, Q. Ren, TM Lowe, J. Maupin-Furlow, M. Pohlschroder, C. Daniels, F. Pfeiffer, T. Allers, JA Eisen: The complete genome sequence of Haloferax volcanii DS2, a model archaeon. In: PLOS ONE . Volume 5, number 3, March 2010, p. E9605, doi : 10.1371 / journal.pone.0009605 , PMID 20333302 , PMC 2841640 (free full text).
  11. ↑ a b S. Delmas, IG Duggin, T. Allers: DNA damage induces nucleoid compaction via the Mre11-Rad50 complex in the archaeon Haloferax volcanii . In: Molecular microbiology. Volume 87, number 1, January 2013, pp. 168–179, doi : 10.1111 / mmi.12091 , PMID 23145964 , PMC 3565448 (free full text)
  12. ↑ a b A. Naor, P. Lapierre, M. Mevarech, RT Papke, U. Gophna: Low species barriers in halophilic archaea and the formation of recombinant hybrids. In: Current biology: CB. Volume 22, Number 15, August 2012, pp. 1444-1448, doi : 10.1016 / j.cub.2012.05.056 , PMID 22748314 .
  13. ↑ S. DasSarma: Extreme Halo Philes Are Models for Astrobiology . In: Microbe Magazine . tape 1 , no. 3 , 2006, p. 120-126 .

Web links

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