Biology:Methanococcus maripaludis
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| Species: | Methanococcus maripaludis Jones et al. 1984
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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]
- Amino acid metabolism
- Glycogen metabolism
- Glycolysis
- Methanogenesis
- Nitrogen metabolism
- Non-oxidative pentose phosphate pathway
- Nucleotide metabolism
- Reductive citric acid (RTCA) cycle
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:
- Reduction of CO2 via methanofuran and reduced ferredoxins[6]
- Oxidation and subsequent reduction of the coenzyme F420 in the presence of H2[7][6]
- Transfer of methyl group from methyl-THMPT to coenzyme M (HS-CoM), driving translocation of 2Na+ across membrane to strengthen the proton gradient[8]
- 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
- ↑ 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.
- ↑ "Characterization of Methanococcus maripaludis sp. nov., a new methanogen isolated from salt marsh sediment". Archives of Microbiology 135 (2): 91–97. 1983. doi:10.1007/BF00408015. ISSN 0302-8933.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 "Metabolic processes of Methanococcus maripaludis and potential applications". Microbial Cell Factories 15 (1): 107. June 2016. doi:10.1186/s12934-016-0500-0. PMID 27286964.
- ↑ "Tetrahydromethanopterin, a carbon carrier in methanogenesis". The Journal of Biological Chemistry 259 (15): 9447–9455. August 1984. doi:10.1016/s0021-9258(17)42721-9. PMID 6547718.
- ↑ "Hydrogenase-independent uptake and metabolism of electrons by the archaeon Methanococcus maripaludis". The ISME Journal 8 (8): 1673–1681. August 2014. doi:10.1038/ismej.2014.82. PMID 24844759.
- ↑ 6.0 6.1 "Methanogenic archaea: ecologically relevant differences in energy conservation". Nature Reviews. Microbiology 6 (8): 579–591. August 2008. doi:10.1038/nrmicro1931. PMID 18587410.
- ↑ "Purification, regulation, and molecular and biochemical characterization of pyruvate carboxylase from Methanobacterium thermoautotrophicum strain deltaH". The Journal of Biological Chemistry 273 (9): 5155–5166. February 1998. doi:10.1074/jbc.273.9.5155. PMID 9478969.
- ↑ "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. February 1992. doi:10.1016/0167-4838(92)90282-i. PMID 1737047.
- ↑ "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. February 2011. doi:10.1073/pnas.1016761108. PMID 21262829. Bibcode: 2011PNAS..108.2981K.
- ↑ 10.0 10.1 "Flagella and pili are both necessary for efficient attachment of Methanococcus maripaludis to surfaces". FEMS Microbiology Letters 319 (1): 44–50. June 2011. doi:10.1111/j.1574-6968.2011.02264.x. PMID 21410509.
Further reading
- "Continuous culture of Methanococcus maripaludis under defined nutrient conditions". FEMS Microbiology Letters 238 (1): 85–91. September 2004. doi:10.1016/j.femsle.2004.07.021. PMID 15336407.
External links
Wikidata ☰ Q16985527 entry
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