User:Njkleb/Methanococcus maripaludis

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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.

Metabolism
The metabolic landscape of M. maripaludis consists of the following major subsystems:


 * Amino acid metabolism - synthesis of amino acids via a variety of biochemical pathways


 * Glycogen metabolism - synthesis, storage, and consumption of glycogen via the Embden-Meyerhoff-Parnas pathway


 * Glycolysis - conversion of acetyl-CoA to pyruvate via pyruvate synthase


 * Methanogenesis - conversion of CO2 and H2 into methane and H2O


 * Nitrogen metabolism - fixation of nitrogen and use for synthesis of certain amino acids
 * Non-oxidative pentose phosphate pathway - synthesis of pentose sugars from glyceraldehyde-3-phosphate and fructose-6-phosphate
 * Nucleotide metabolism - synthesis of nucleotides and nucleic acids via products of pentose phosphate pathway
 * Reductive citric acid (RTCA) cycle - synthesis of carbon compounds from pyruvate, H2O, and CO2

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:


 * 1) Reduction of CO2 via methanofuran and reduced ferredoxins
 * 2) Oxidation and subsequent reduction of the coenzyme F420 in the presence of H2
 * 3) Transfer of methyl group from methyl-THMPT to coenzyme M (HS-CoM), driving translocation of 2Na+ across membrane to strengthen proton gradient
 * 4) 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 is an S-layer that does not contain peptidoglycan; which helps to identify its domain as archaea. It can grow both flagella and pili. Flagella helps with motility around its surrounding environment, but the main usage of pili in this particular strand is still unknown. These cells use both flagella and pili in order to attach to different surfaces, meaning that if they encounter a desirable environment, they will be able to become stationary in that area. This was tested by noting that strains of the cell that weren't able to grow these attachments struggled stay in one place when placed into preferable temperatures and pH levels.

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 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.

Antibiotic resistance
Certain strains of Methanococcus maripaludis, such as S2, have demonstrated resistance to common antibiotics such as echinomycin and neomycin. The region between genes mmp0478 and mmp0479 has been associated with resistance to echinomycin, but these genes' exact function has not yet been identified. Identified families of enzymes responsible for neomycin resistance, O-phosphotransferase, O-adenyltranferases and N-acetyltransferases, are not present in M. maripaludis. However, the protein MMP0535 has been associated with neomycin-resistant mutants of M. maripaludis despite its function remaining unidentified. Furthermore, neomycin-resistant mutants of M. maripaludis have both been associated with mutations in enzymes geranylgeranylglyceryl phosphate synthase (MMP0007), transketolase (MMP1115) and ComE (MMP1689). These enzymes have known functions in regard to membrane biosynthesis, carbohydrate metabolism and cofactor biosynthesis. However, their role in Methanococcus maripaludis resistance to neomycin remains unknown.

Culturing
Due to the anaerobic nature of this microbe, there are certain measures that must be taken in order to culture and perform experiments with M. maripaludis. Whenever the test tubes are opened, they must remain in anaerobic conditions, which is achieved by opening the airtight vessels in an anaerobic chamber with fewer than 100 ppm of oxygen. For experiments that require heating or sterilization, a traditional flame can not be used due to the lack of oxygen, so instead a strong electric current can be run through a wire to generate heat. When storing and working with these microbes, many labs use resazurin, which turns pink in the presence of oxygen, to ensure that no compromised samples are used for experimentation.

Environmental Role/Impacts
Methanogens together have many impacts on waste water treatment, carbon conversion, hydrogen production, and many other environmental impacts. M. maripaludis has many potential applications, but has not been used in the same way as other methanogens. Methanogens have been used in waste water treatment by anaerobically degrading waste to produce a biogas of methane and this happens by a symbiotic relationship between syntrophic bacteria. There are many possible waste reducing applications that M. maripaludis could be used in many but the research is not developed to prove how beneficial it would be. These applications would include reducing carbon emissions and they could be studied/used in pharmaceuticals. One large issue with using methanogens with these environmental concerns is the need for high amounts of H2 for a large scale of biomethane production.

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