Candidatus "Methylomirabilis oxyfera" is a candidate species of Gram-negative bacteria belonging to the NC10 phylum, characterized for its capacity to couple anaerobic methane oxidation with nitrite reduction in anoxic environments.[3][4] To acquire oxygen for methane oxidation, M. oxyfera utilizes an intra-aerobic pathway through the reduction of nitrite (NO2) to dinitrogen (N2) and oxygen.[5]
Enrichment
Enriched Ca. "M. oxyfera" cells have been identified as primarily having a unique polygonal cell shape through the use of electron microscopy techniques. Unlike methanotrophicPseudomonadota, Ca. "M. oxyfera" cells lack intracytoplasmic membranes when grown under laboratory conditions.[6] The optimum growth ranges for Ca. "M. oxyfera" is between pH 7-8 and 25-30 °C.[3]Ca. "M. oxyfera"cell envelopes are Gram-negative and are generally 0.25–0.5 μm in diameter and 0.8–1.1 μm in length.[3][6]
Methane oxidation
Ca. "M. oxyfera" has the capacity to disproportionate nitric oxide into oxygen and nitrogen gas. This intermediate oxygen is then used in the oxidation of methane into carbon dioxide.[3][5]
Overall reactions
Nitrogen oxide dismutation:
2 NO−2 → 2 NO → N2 + O2
Methane oxidation:
O2 + CH4 → CH3OH → CO2
Environmental significance
Ca. "M. oxyfera" has been identified in several environments including rice paddy soil in China,[7] multiple river and lake sediments,[8] and wastewater sludge in The Netherlands.[9]Ca. "M. oxyfera" is predicted to inhabit environments with high concentrations of nitrogen and methane, near boundaries that separate oxic and anoxic zones. It is suggested that Ca. "M. oxyfera" and similar organisms contribute to the global carbon and nitrogen cycles. These organisms may also play a role in reducing the nutrient loads within freshwater ecosystems that have been contaminated with fertilizers.[8] Nitrites are usually undesirable in the environment, can be detrimental to human health, and can lead to eutrophication of aquatic ecosystems and algal blooms.[10][11] Meanwhile methane is a potent greenhouse gas that has a stronger greenhouse potential per molecule than carbon dioxide.[12] The presence of organisms like M. oxyfera can therefore be beneficial in many environments and might be used for bioremediation or sewage treatment in the future.
^ abCabrol, Léa; Thalasso, Frédéric; Gandois, Laure; Sepulveda-Jauregui, Armando; Martinez-Cruz, Karla; Teisserenc, Roman; Tananaev, Nikita; Tveit, Alexander; Svenning, Mette M.; Barret, Maialen (September 2020). "Anaerobic oxidation of methane and associated microbiome in anoxic water of Northwestern Siberian lakes". Science of the Total Environment. 736: 139588. Bibcode:2020ScTEn.73639588C. doi:10.1016/j.scitotenv.2020.139588. hdl:10037/19970. PMID32497884.
^ abcdEttwig, Katharina F.; Butler, Margaret K.; Le Paslier, Denis; Pelletier, Eric; Mangenot, Sophie; Kuypers, Marcel M. M.; Schreiber, Frank; Dutilh, Bas E.; Zedelius, Johannes; de Beer, Dirk; Gloerich, Jolein; Wessels, Hans J. C. T.; van Alen, Theo; Luesken, Francisca; Wu, Ming L.; van de Pas-Schoonen, Katinka T.; Op den Camp, Huub J. M.; Janssen-Megens, Eva M.; Francoijs, Kees-Jan; Stunnenberg, Henk; Weissenbach, Jean; Jetten, Mike S. M.; Strous, Marc (March 2010). "Nitrite-driven anaerobic methane oxidation by oxygenic bacteria". Nature. 464 (7288): 543–548. Bibcode:2010Natur.464..543E. doi:10.1038/nature08883. hdl:2066/84284. PMID20336137. S2CID205220000.
^Haroon, Mohamed F.; Hu, Shihu; Shi, Ying; Imelfort, Michael; Keller, Jurg; Hugenholtz, Philip; Yuan, Zhiguo; Tyson, Gene W. (29 August 2013). "Anaerobic oxidation of methane coupled to nitrate reduction in a novel archaeal lineage". Nature. 500 (7464): 567–570. Bibcode:2013Natur.500..567H. doi:10.1038/nature12375. PMID23892779. S2CID4368118.
^ abWu, Ming L.; Ettwig, Katharina F.; Jetten, Mike S.M.; Strous, Marc; Keltjens, Jan T.; Niftrik, Laura van (February 2011). "A new intra-aerobic metabolism in the nitrite-dependent anaerobic methane-oxidizing bacterium Candidatus 'Methylomirabilis oxyfera'". Biochemical Society Transactions. 39 (1): 243–248. doi:10.1042/BST0390243. hdl:2066/91512. PMID21265781.
