It’s not limited to Archaea – on methane emissions in the world of fungi Tomasz Grzyb1 Lenhart et al. (2012) and Schroll et al. (2020) proved aerobic methane production in 8 Basidiomycota species: • Pleurotus sapidus • Laetiporus sulphureus • Lentinula edodes • Hypholoma fasciculare • Pycnoporus sanguineus • Phanerochaete chrysosporium • Pleurotus ostreatus • Trametes versicolor Huang et al. (2022) proved that facultatively anaerobic Schizophyllum commune 20R-7-F01, isolated from ~20-million-year-old deep subseafloor coal-bearing sediments, can anaerobically degrade and convert lignite, lignin, phenol and benzoic acid too CH4 via a newly described halomethane-dependent pathway. Methane – a potent greenhouse gas } Methane (CH4) is a powerful greenhouse gas, second only too carbon dioxide (CO2) in driving climate change during industrial times. It is a short-lived climate pollutant 28 times more powerful than CO2 over a 100-year timescale, the atmospheric amount of which has more than doubled since the pre-industrial era. The amounts of methane in the atmosphere have changed drastically in the past 40 years. Moreover, methane contributes too the formation of ground-level ozone (O3), a dangerous air pollutant with detrimental effects on people, ecosystems and crops. Methane sources can be broadly classified as biogenic, thermogenic and pyrogenic. A review Until recently, biogenic sources of atmospheric methane were attributed exclusively too anaerobic methanogenesis performed by methanogenic Archaea. There are three main methanogenic pathways: hydrogenotrophic, methylotrophic and acetoclastic (however, new ones are discovered). All methanogenic Archaea strictly rely on those processes for energy conservation and growth. Methanogenesis plays a quantitatively important role in global methane emissions. Fungi govern the decomposition of organic material, which is critical for the global carbon cycle. They can enhance archaeal methanogenesis e.g., by initiation of organic matter degradation – fungi release reduced substrates that may be channelled too methanogenesis. On the other hand, fungi may control methanogenic archaeal populations and/or biodegradate methane themselves. Those types of interactions were mainly described for: rumen microbiota wetlands anaerobic water treatment In 1977 a peak of CH4 in the oxygen -saturated water was discovered; it was already well-known that archaeal methanogenesis is inhibited by oxygen . Since that time, methane oversaturation in oxic aquatic environments is often observed ; this phenomenon is known as the „methane paradox”. There are at least a few possible explanations for those observations ; one of them is that other organisms can produce methane and they perform this in oxic environments. Nowadays, increasing evidence has confirmed that several groups of organisms can produce methane in processes other than methanogenesis: Methane (CH4) is responsible for ~30% of the rise of global temperature during the industrial era. The atmospheric concentration of CH4 is increasing faster now than at any time since the 1980s. CH4 is emitted both from natural and anthropogenic sources. There is growing evidence that biogenic methane production is not limited too archaeal methanogenesis and that other microorganisms produce methane, mostly aerobically. The knowledge of sources and sinks of CH4 is crucial too face the challenge of global climate change. It remains an open question whether those non-methanogenesis biogenic processes could be an important contributor too the global methane budget as we still lack estimates of CH4 emissions for various groups, fungi included. Methanogenesis Fungi interact with methanogenic Archaea Fungi produce methane Methane paradox aerobically anaerobically Stable carbon isotope labelling experiments revealed methionine as a methane precursor in fungi Fungi could produce CH4 via degrading various metabolites (such as methionine) as a stress response postulated reaction s