AN INVESTIGATION OF THE EFFECTS OF CORRINOID STRUCTURE ON THE METHANOGENESIS PATHWAY IN <i>METHANOSARCINA BARKERI</i> STRAIN <i>FUSARO</i>

Methane is responsible for at least 10% of greenhouse gas emissions in the United States alone, and although not the most abundant, it is one of the most dangerously potent greenhouse gases. Methanogens are microbial organisms that require a corrinoid cofactor to synthesize methane.Previous work in bacteria has demonstrated that corrinoid mediated processes, such as methyl transfers, are directly influenced by the structure of the corrinoid cofactor1; 2; 3. Individual organisms show bias or preference for one structure over another, with the sole difference being the lower ligand attached to the corrin ring4. Most organisms have a "preferred" corrinoid structure, and when this structure is not available, are forced to use an alternative corrinoid. In some cases, the alternative corrinoid can slow down the organisms metabolic process, while in other cases, the alternative corrinoid cannot be used at all. Availability of corrinoids and their precursors have serious implications on microbial metabolism, and the ability of a microbe to occupy its niche5.In methanogenesis, the corrinoid enzyme complex involved in the methyl transfer varies based on the carbon starting material:In the acetate and CO2 pathways, the methyl group of methyl-tetrahydramethanopterin (methyl-H₄SPT) is transferred to an 8-subunit transmembrane protein. Subunit A contains the corrinoid prosthetic group.In the methanol conversion pathway, the corrinoid cofactor is part of a cytoplasmic enzyme complex.Unlike most organisms requiring corrinoid cofactors, methanogens can synthesize their own lower bases. However, if there are other lower bases present in the environment, they will use those instead. Due to the importance of corrinoid structure to microbial metabolism, we believe that corrinoid structure in methanogens could affect methanogenesis.Synthetic lower bases could affect the ability of the corrinoid cofactor to properly bind to its enzyme/protein complex, thus affecting the ability for the remaining two steps of the methanogenesis pathway to occur. Finding a way to slow methane production has potential applications in the agricultural industry, which could lower our contributions to global warming.