Methanohalophilus mahii

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Methanohalophilus mahii
Methanohalophilus mahii SLP.jpg
Scanning electron microscope image of Mhp. mahii SLP
Scientific classification
Domain:
Archaea
Kingdom:
Euryarchaeota
Phylum:
Euryarchaeota
Class:
Methanomicrobia
Order:
Methanosarcinales
Family:
Methanosarcinaceae
Genus:
Methanohalophilus
Species:
M. mahii
Binomial name
Methanohalophilus mahii
Paterek and Smith (1988)

Methanohalophilus mahii (also known as Mhp. mahii) is an obligately anaerobic, [1] methylotrophic, [2] methanogenic [1] cocci-shaped [2] archaeon of the genus Methanohalophilus [2] that can be found in high salinity aquatic environments. [1] The name Methanohalophilus is said to be derived from methanum meaning "methane" in Latin; halo meaning "salt" in Greek; and mahii meaning "of Mah" in Latin, after R.A. Mah, who did substantial amounts of research on aerobic and methanogenic microbes. [2] The proper word in ancient Greek for "salt" is however hals (ἅλς). [3] The specific strain type was designated SLP (= ATCC 35705) and is currently the only identified strain of this species. [2]

Contents

Phylogeny

There are a total of four species in the genus Methanohalophilus including Methanohalophilus mahii, Methanohalophilus halophilus, Methanohalophilus portucalensis, and Methanohalophilus euhalobius. [1] The closest relative, Methanohalophilus portucalensis, has a 99.8% similarity in sequence across the whole genome to Methanohalophilus mahii. [1] The other Methanohalophilus species have less than a 94.7% similarity to Methanohalophilus mahii. [1] All species in the genus are halophilic methanogens that contribute to marine ecosystem mineral cycling. [1]

Discovery

In 1988, Robert Paterek and Paul Smith were searching for methanogenic bacteria in the Great Salt Lake in Utah when they first discovered the archaeon Methanohalophilus mahii in its anoxic sediments. [2] Sediment samples were collected and stored in plexiglas tubes, and sub-core samples taken with a brass cork borer and transferred to fifty milliliter serum bottles. [4] All samples were processed within forty-eight hours of collection. [4] The media used for isolation of Methanohalophilus mahii colonies was prepared using the Hungate technique for proper isolation of anaerobic microbes. [4] Serial dilutions were prepared in a 1:10 ratio, [4] and agar roll tubes were inoculated and incubated at 30 °C for eight weeks. [4] Isolated methanogenic colonies were chosen by identifying those with a foamy texture, denoting gas release, [1] and repeatedly diluted and inoculated on agar roll tubes until only one type of colony morphology remained. [4] These colonies appeared as cream to pale yellow-colored circular-shaped colonies with an overall foamy texture due to gas release. [2]

Cell Culture

Several analyses were done to determine cell characteristics. [4] Methanohalophilus mahii is classified as a moderate halophile, or an organism that can grow in high salinity environments, since it can grow anywhere from a 0.5 to 3.5 M NaCl range, [1] with an optimal growth concentration at 2.0 M NaCl, [1] but with a 1.2 M NaCl concentration yielding the highest culture density. [1] It can also grow in varying pH levels ranging from 6.5 to 8.2, [1] with an optimum pH of 7.5. [1] Methanohalophilus mahii is a mesophile, or an organism that thrives at moderate temperatures, and grows best at a temperature of 37 °C. [2]

Cell Structure

Methanohalophilus mahii cells stain Gram negative, [1] and are non-motile, [2] irregular cocci [2] approximately 0.8 to 1.8 micrometers in diameter. [2] Additionally, the cells fluoresce under 420 nanometer light. [2] Membrane phospholipids are composed of β-hydroxyarchaeol cores, glucose glycolipids, and ethanolamine, glycerol, and myo-inositol polar head groups. [1]

Metabolism

Methanohalophilus mahii is an obligately anaerobic [1] methylotrophic [2] and methanogenic chemoheterotroph, able to reduce single-carbon compounds and multi-carbon compounds given that there are no carbon-carbon double bonds present. [1] Trace amounts of Mg2 +, K+, Ca2+, and Fe2+ ions are required for methanogenic growth. [1] Methanol can be used independently as a carbon source, and the Embden-Meyerhof-Parnas (EMP) glycolytic pathway can be utilized for catabolic processes. [1] Possible electron donors include methanol, methylamines, dimethylamines, and trimethylamines. [1] Methanohalophilus mahii is capable of utilizing several metabolic pathways to either reduce or oxidize methyl groups, creating either methane or carbon dioxide in the process. [1] In the reductive methylotrophic methanogenic pathway, Methanohalophilus mahii can eventually reduce a methyl group to a methane, which is released. [1] In the oxidative methylotrophic pathway, the methyl group is instead oxidized to carbon dioxide and released. [1] This process directly contributes to carbon mineralization in marine ecosystems. [1]

Genome

Methanohalophilus mahii’s genome was sequenced through shotgun sequencing using a 6.8 kilobase Sanger DNA library. [1] The complete genome size was determined to be 2,012,424 base pairs long, with 2,906 total genes, and 2,032 actual protein-coding genes. [1] The sequence had a 42.6% GC content, and forty-five pseudogenes were located. [1]

Importance

Methanohalophilus mahii has a unique suppressor tRNA with a modified pyrrolysine, an amino acid that is most commonly found in prokaryotes, that can recognize and bind to the amber STOP codon (UAG) which is also coded for by the genes used for methylamine methyltransferases. [1] This species was also the first member to have its genome completely sequenced in the genus Methanohalophilus[1] , which comprises mildly halophilic, methylotrophic methanogens. [1] These archaea in general are known to greatly contribute to the carbon mineralization process in marine ecosystems. [1] Specifically, the oxidative methylotrophic pathway Methanohalophilus mahii utilizes allows the species to oxidize methane to carbon dioxide, which, in turn, is used by other plants and organisms. [1] This mineral cycling process allows for more growth and diversity in the ocean. [1]

Related Research Articles

Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They belong to the domain Archaea and are members of the phylum Euryarchaeota. Methanogens are common in wetlands, where they are responsible for marsh gas, and can occur in the digestive tracts of animals including ruminants and humans, where they are responsible for the methane content of belching and flatulence. In marine sediments, the biological production of methane, termed methanogenesis, is generally confined to where sulfates are depleted below the top layers and methanogens play an indispensable role in anaerobic wastewater treatments. Other methanogens are extremophiles, found in environments such as hot springs and submarine hydrothermal vents as well as in the "solid" rock of Earth's crust, kilometers below the surface.

Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. Organisms capable of producing methane for energy conservation have been identified only from the domain Archaea, a group phylogenetically distinct from both eukaryotes and bacteria, although many live in close association with anaerobic bacteria. The production of methane is an important and widespread form of microbial metabolism. In anoxic environments, it is the final step in the decomposition of biomass. Methanogenesis is responsible for significant amounts of natural gas accumulations, the remainder being thermogenic.

Methanotrophs are prokaryotes that metabolize methane as their source of carbon and chemical energy. They are bacteria or archaea, can grow aerobically or anaerobically, and require single-carbon compounds to survive.

Archaeoglobus is a genus of the phylum Euryarchaeota. Archaeoglobus can be found in high-temperature oil fields where they may contribute to oil field souring.

<i>Methanosarcina</i> Genus of archaea

Methanosarcina is a genus of euryarchaeote archaea that produce methane. These single-celled organisms are known as anaerobic methanogens that produce methane using all three metabolic pathways for methanogenesis. They live in diverse environments where they can remain safe from the effects of oxygen, whether on the earth's surface, in groundwater, in deep sea vents, and in animal digestive tracts. Methanosarcina grow in colonies.

Microbial metabolism is the means by which a microbe obtains the energy and nutrients it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles.

In biology, syntrophy, synthrophy, or cross-feeding is the phenomenon of one species feeding on the metabolic products of another species to cope up with the energy limitations by electron transfer. In this type of biological interaction, metabolite transfer happens between two or more metabolically diverse microbial species that live in close proximity to each other. The growth of one partner depends on the nutrients, growth factors, or substrates provided by the other partner. Thus, syntrophism can be considered as an obligatory interdependency and a mutualistic metabolism between two different bacterial species.

In taxonomy, Methanococcoides is a genus of the Methanosarcinaceae.

Methanogenium boonei is a methanogenic archaean. Cells are non-motile irregular cocci 1.0–2.5 μm in diameter. This mesophile grows optimally at 19.4 °C, pH6.4–7.8, salinity 0.3–0.5M Na+. It was first isolated from Skan Bay, Alaska.

In taxonomy, Methanimicrococcus is a genus of the Methanosarcinaceae. The members of this genus have been found in pharmaceutical wastewater, and they can contribute to the degradation of organic contaminants.

In taxonomy, Methanohalobium is a genus of the Methanosarcinaceae. Its genome has been sequenced. The genus contains one species, M. evestigatum.

<i>Methanohalophilus</i> Genus of archaea

In taxonomy, Methanohalophilus is a genus of the Methanosarcinaceae.

In taxonomy, Methanolobus is a genus of methanogenic archaea within the Methanosarcinaceae. These organisms are strictly anaerobes and live exclusively through the production of methane, but the species within Methanolobus cannot use carbon dioxide with hydrogen, acetate or formate, only methyl compounds. The cells are irregular coccoid in form and approximately 1 μm in diameter. They do not form endospores. They are Gram negative and only some are motile, via a single flagellum. They are found in lake and ocean sediments that lack oxygen.

In taxonomy, Methanocorpusculum is a genus of microbes within the family Methanocorpusculaceae. The species within Methanocorpusculum were first isolated from biodisgester wastewater and activated sludge from anaerobic digestors. In nature, they live in freshwater environments. Unlike most other methanogenic archaea, they do not require high temperatures or extreme salt concentrations to live and grow.

Methanocaldococcus jannaschii is a thermophilic methanogenic archaean in the class Methanococci. It was the first archaeon, and third organism, to have its complete genome sequenced. The sequencing identified many genes unique to the archaea. Many of the synthesis pathways for methanogenic cofactors were worked out biochemically in this organism, as were several other archaeal-specific metabolic pathways.

Methanococcoides burtonii is a methylotrophic methanogenic archaeon first isolated from Ace Lake, Antarctica. Its type strain is DSM 6242.

Methanococcus maripaludis is a species of methanogenic archaea found in marine environments, predominantly salt marshes. M. maripaludis is a weakly motile, non-spore-forming, Gram-negative, strict anaerobic mesophile with a pleomorphic coccoid-rod shape, averaging 1.2 by 1.6 μm is size. The genome of M. maripaludis has been sequenced, and over 1,700 protein-coding genes have been identified. In ideal conditions, M. maripaludis grows quickly and can double every two hours.

<i>Methanosarcina barkeri</i> Species of archaeon

Methanosarcina barkeri is the most fundamental species of the genus Methanosarcina, and their properties apply generally to the genus Methanosarcina. Methanosarcina barkeri can produce methane anaerobically through different metabolic pathways. M. barkeri can subsume a variety of molecules for ATP production, including methanol, acetate, methylamines, and different forms of hydrogen and carbon dioxide. Although it is a slow developer and is sensitive to change in environmental conditions, M. barkeri is able to grow in a variety of different substrates, adding to its appeal for genetic analysis. Additionally, M. barkeri is the first organism in which the amino acid pyrrolysine was found. Furthermore, two strains of M. barkeri, M. b. Fusaro and M. b. MS have been identified to possess an F-type ATPase along with an A-type ATPase.

Hydrogenotrophs are organisms that are able to metabolize molecular hydrogen as a source of energy.

Biological methanation (also: biological hydrogen methanation (BHM) or microbiological methanation) is a conversion process to generate methane by means of highly specialized microorganisms (Archaea) within a technical system. This process can be applied in a power-to-gas system to produce biomethane and is appreciated as an important storage technology for variable renewable energy in the context of energy transition. This technology was successfully implemented at a first power-to-gas plant of that kind in the year 2015.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Spring, S.; Scheuner, C.; Lapidus, A.; Lucas, S.; Rio, T. G. D.; Tice, H.; Copeland, A.; Cheng, J.; Chen, F. (2010-12-23). "The Genome Sequence of Methanohalophilus mahii SLPT Reveals Differences in the Energy Metabolism among Members of the Methanosarcinaceae Inhabiting Freshwater and Saline Environments". Archaea. 2010: 690737. doi: 10.1155/2010/690737 . ISSN   1472-3646. PMC   3017947 . PMID   21234345.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 Paterek, J. R.; Smith, P. H. (1988-01-01). "Methanohalophilus mahii gen. nov., sp. nov., a Methylotrophic Halophilic Methanogen". International Journal of Systematic and Evolutionary Microbiology. 38 (1): 122–123. doi: 10.1099/00207713-38-1-122 .
  3. ↑ Liddell, H.G. & Scott, R. (1940). A Greek-English Lexicon revised and augmented throughout by Sir Henry Stuart Jones with the assistance of. Roderick McKenzie. Oxford: Clarendon Press.
  4. 1 2 3 4 5 6 7 Paterek, J. Robert; Smith, Paul H. (1985-10-01). "Isolation and Characterization of a Halophilic Methanogen from Great Salt Lake". Applied and Environmental Microbiology. 50 (4): 877–881. doi:10.1128/aem.50.4.877-881.1985. ISSN   0099-2240. PMC   291763 . PMID   16346919.

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