Methanococcus maripaludis
Scientific classification
Domain:
Archaea
Kingdom:
Euryarchaeota
Phylum:
Euryarchaeota
Class:
Methanococci
Order:
Methanococcales
Family:
Methanococcaceae
Genus:
Methanococcus
Species:
Methanococcus maripaludis

Jones et al. 1984

Methanococcus maripaludis is a species of methanogenic archaea found in marine environments, predominantly salt marshes.[1] 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.[2] The genome of M. maripaludis has been sequenced, and over 1,700 protein-coding genes have been identified.[3] In ideal conditions, M. maripaludis grows quickly and can double every two hours.[3]

Metabolism

The metabolic landscape of M. maripaludis consists of eight major subsystems:[3]

Methanogenesis

In M. maripaludis, the primary carbon source for methanogenesis is carbon dioxide, although alternatives such as formate are also used. Though all methanogens utilize certain key coenzymes, cofactors, and intermediates to produce methane, M. maripaludis undergoes the Wolfe cycle, which converts CO2 and hydrogen gas into methane and H2O.[4] Some strains and mutants of M. maripaludis have been shown to be capable of methanogenesis in the absence of hydrogen gas, though this is uncommon.[5]

Methanogenesis in M. maripaludis occurs in the following steps:

  1. Reduction of CO2 via methanofuran and reduced ferredoxins[6]
  2. Oxidation and subsequent reduction of the coenzyme F420 in the presence of H2[7][6]
  3. Transfer of methyl group from methyl-THMPT to coenzyme M (HS-CoM), driving translocation of 2Na+ across membrane to strengthen the proton gradient[8]
  4. Demethylation of methyl-S-CoM to form methane and generate additional energy via subsequent reduction of byproducts with H2[9]

Cell structure

The cell wall of Methanococcus maripaludis has an S-layer that does not contain peptidoglycan, which helps to identify its domain as Archaea.[3] It has flagella, which confer motility, and pili.[10] These cells use both flagella and pili to attach to surfaces, meaning that if they encounter a desirable environment, they can remain there.[10]

Genetic characteristics

Methanococcus maripaludis is one of four hydrogenotrophic methanogens, along with Methanocaldococcus jannaschii, Methanothermobacter thermautotrophicus, and Methanopyrus kandleri, to have its genome sequenced.[3] Of these four, Methanocaldococcus jannaschii is the closest living, known relative of M. maripaludis. M. maripaludis, like many other archaea, has one single circular chromosome.[3] Of its 1,722 protein coding genes, 835 ORFs, or open reading frames, have unknown functions, and 129 ORFs are unique to M. maripaludis.[3] According to the number of BlastP hits, or similar protein sequences identified by the Basic Local Alignment Search Tool (BLAST), in the genome sequence, M. maripaludis is similar to most other methanogens.[3] However, M. maripaludis is missing certain features present in most methanogens, such as the ribulose bisphosphate carboxylase enzyme.[3]

Environmental roles

Methanogens play important roles in waste water treatment, carbon conversion, hydrogen production, and many other environmental processes.[3] For example, methanogens have been used in waste water treatment by anaerobically degrading waste to produce methane in a symbiotic relationship with syntrophic bacteria.[3] M. maripaludis has similar potential applications but an issue with using methanogens for biomethane production is the need for high amounts of hydrogen.[3]

References

  1. ^ Populations of methanogenic bacteria in a georgia salt marsh. Applied and Environmental Microbiology. May 1988;54(5):1151–7. doi:10.1128/aem.54.5.1151-1157.1988. PMID 16347628.
  2. ^ Jones WJ, Paynter MJ, Gupta R (1983). "Characterization of Methanococcus maripaludis sp. nov., a new methanogen isolated from salt marsh sediment". Archives of Microbiology. 135 (2): 91–97. doi:10.1007/BF00408015. ISSN 0302-8933. S2CID 2025112.
  3. ^ a b c d e f g h i j k l Goyal N, Zhou Z, Karimi IA (June 2016). "Metabolic processes of Methanococcus maripaludis and potential applications". Microbial Cell Factories. 15 (1): 107. doi:10.1186/s12934-016-0500-0. PMC 4902934. PMID 27286964.
  4. ^ Escalante-Semerena JC, Rinehart KL, Wolfe RS (August 1984). "Tetrahydromethanopterin, a carbon carrier in methanogenesis". The Journal of Biological Chemistry. 259 (15): 9447–9455. doi:10.1016/s0021-9258(17)42721-9. PMID 6547718.
  5. ^ Lohner ST, Deutzmann JS, Logan BE, Leigh J, Spormann AM (August 2014). "Hydrogenase-independent uptake and metabolism of electrons by the archaeon Methanococcus maripaludis". The ISME Journal. 8 (8): 1673–1681. doi:10.1038/ismej.2014.82. PMC 4817615. PMID 24844759.
  6. ^ a b Thauer RK, Kaster AK, Seedorf H, Buckel W, Hedderich R (August 2008). "Methanogenic archaea: ecologically relevant differences in energy conservation". Nature Reviews. Microbiology. 6 (8): 579–591. doi:10.1038/nrmicro1931. PMID 18587410. S2CID 32698014.
  7. ^ Mukhopadhyay B, Stoddard SF, Wolfe RS (February 1998). "Purification, regulation, and molecular and biochemical characterization of pyruvate carboxylase from Methanobacterium thermoautotrophicum strain deltaH". The Journal of Biological Chemistry. 273 (9): 5155–5166. doi:10.1074/jbc.273.9.5155. PMID 9478969.
  8. ^ Kengen SW, Daas PJ, Duits EF, Keltjens JT, van der Drift C, Vogels GD (February 1992). "Isolation of a 5-hydroxybenzimidazolyl cobamide-containing enzyme involved in the methyltetrahydromethanopterin: coenzyme M methyltransferase reaction in Methanobacterium thermoautotrophicum". Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology. 1118 (3): 249–260. doi:10.1016/0167-4838(92)90282-i. PMID 1737047.
  9. ^ Kaster AK, Moll J, Parey K, Thauer RK (February 2011). "Coupling of ferredoxin and heterodisulfide reduction via electron bifurcation in hydrogenotrophic methanogenic archaea". Proceedings of the National Academy of Sciences of the United States of America. 108 (7): 2981–2986. Bibcode:2011PNAS..108.2981K. doi:10.1073/pnas.1016761108. PMC 3041090. PMID 21262829.
  10. ^ a b Jarrell KF, Stark M, Nair DB, Chong JP (June 2011). "Flagella and pili are both necessary for efficient attachment of Methanococcus maripaludis to surfaces". FEMS Microbiology Letters. 319 (1): 44–50. doi:10.1111/j.1574-6968.2011.02264.x. PMID 21410509. S2CID 36895781.

Further reading

  • Haydock AK, Porat I, Whitman WB, Leigh JA (September 2004). "Continuous culture of Methanococcus maripaludis under defined nutrient conditions". FEMS Microbiology Letters. 238 (1): 85–91. doi:10.1016/j.femsle.2004.07.021. PMID 15336407.

External links

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