Methanococcus maripaludis is a species of methanogenic archaea found in marine environments, predominantly salt marshes.

[3] This archaeon has a pleomorphic coccoid-rod shape of 1.2 by 1.6 μm, in average size, and has many unique metabolic processes that aid in survival.

[4] The metabolic landscape of M. maripaludis consists of eight major subsystems which provide pathways for energy generation and cell growth.

[4] Methanogenesis, the process of reducing carbon dioxide to methane, serves as the primary pathway for energy generation using coenzymes and a membrane-bound enzyme complex.

[4] Additionally, the subsystems use two essential intermediates, acetyl CoA and pyruvate, to produce precursors critical for cell growth.

Additionally, the protein kinases, responsible for transferring phosphate groups between compounds, uniquely rely on ADP rather than ATP.

[4] Due to experimentally observed activities of enzymes involved in both the catabolic and anabolic directions of the EMP Pathway, the latter is utilized to a higher extent, resulting in the formation of glycogen stores.

[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.

[4] To synthesize the purines, inosinic acid (IMP) is first made via a series of reactions, which include PRPP combining with glutamine to form 5-phosphoribosylamine.

It plays an essential role in energy production and biosynthesis by generating electron carriers such as NADH and FAD.

[4] M. maripaludis, a strictly anaerobic mesophile, undergoes an incomplete Reductive Citric Acid (RTA) Cycle to reduce CO2 and H2O and synthesize complex carbon molecules.

[4] Lacking several steps and essential enzymes, including phosphoenolpyruvate carboxykinase, citrate synthase, aconitate, and isocitrate dehydrogenase, hinders the completion of this cycle.

The irregular-shaped, weakly-motile coccus, Methanococcus maripaludis, has a diameter of 0.9-1.3 μm with a single, electron-dense S-layer lacking peptidoglycan.

[4] Commonly found in methanogens, their cell walls lack murein and ether-linked membrane lipids, among other biochemical properties.

[4] Archaeal flagella contain distinctive prokaryotic motility structures that are similar to bacterial type IV pili (T4P).

[19][20] The two pilin-like genes, MMP0236 (epdB) and MMP0237 (epdC), possess a short, atypical signal peptide ending in a conserved glycine.

[20] Methanococcus maripaludis is one of four hydrogenotrophic methanogens, along with Methanocaldococcus jannaschii, Methanothermobacter thermautotrophicus, and Methanopyrus kandleri, to have its genome sequenced.

[21] Methanogens play important roles in waste water treatment, carbon conversion, hydrogen production, and many other environmental processes.

[4] M. maripaludis, in addition to other methanogens, has the potential for generating fuels, such as methane and methanol, from CO2 emissions due to native CO2 uptake.

The ability of M. maripaludis to uptake CO2 from the environment in the presence of N2 allows for a potential route for conversion of CO2 emissions to a useful fuel like methane.