Methanococcus maripaludis is a species of methanogenic archaea found in marine environments, predominantly salt marshes. Methanococcus 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. It has been described as an electric bacteria. Methanococcus maripaludis grows quickly and doubles in two hours.
Metabolism
The metabolic landscape of M. maripaludis consists of eight major subsystems:
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 viable. The Wolfe cycle is a cyclic pathway by which CO2 and hydrogen gas are converted into methane and H2O. 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.
Methanogenesis in M. maripaludis occurs in the following steps:
Reduction of CO2 via methanofuran and reduced ferredoxins
Oxidation and subsequent reduction of the coenzyme F420 in the presence of H2
Transfer of methyl group from methyl-THMPT to coenzyme M (HS-CoM), driving translocation of 2Na+ across membrane to strengthen the proton gradient Demethylation of methyl-S-CoM to form methane and generate additional energy via subsequent reduction of byproducts with H2
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. It has flagella, which confer motility, and pili. These cells use both flagella and pili to attach to surfaces, meaning that if they encounter a desirable environment, they can remain there.
Genetic characteristics
Methanococcus maripaludis is one of four hydrogenotrophic methanogens, along with Methanocaldococcus jannaschii, Methanothermobacter thermautotrophicus, and Methanopyrus kandleri, to have its genome sequenced. 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. Of its 1,722 protein coding genes, 835 ORFs, or open reading frames, have unknown functions, and 129 ORFs are unique to M. maripaludis. 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. However, M. maripaludis is missing certain features present in most methanogens, such as the ribulose bisphosphate carboxylase enzyme.
References
Further reading
External links
LPSN
Type strain of Methanococcus maripaludis at BacDive - the Bacterial Diversity Metadatabase