Methanotrophy in Acidic Soils, Including Northern Peatlands

Methane oxidizing microorganisms are present and active in diverse acidic environments including peatlands, geothermal areas, and forest soils. Methanotrophic communities in acidic environments have been examined using cultivation-based physiological analyses as well as cultivation-independent molecular approaches, including omic-technologies. Most investigations have focused on moderately acidophilic, aerobic methanotrophs belonging to the phylum Proteobacteria that are capable of growth as low as pH 4. However, some Verrucomicrobia are capable of oxidizingmethane aerobically at pH 1. Alphaproteobacteria methanotrophs generally dominate the methanotrophic communities in acidic oligotrophic bogs, while Gammaproteobacteria methanotrophs are more predominant in minerotrophic fens. The Verrucomicrobia methanotrophs appear to be limited to geothermal or sulfidic environments. Recent evidence has suggested that anaerobic methane oxidation may also be important in acidic peatland environments. The known diversity and metabolic potential of aerobic and anaerobic methanotrophs that are active under acidic conditions has advanced in recent years. This chapter will summarize cultivation, molecular ecology, taxonomy, and physiology studies of acidophilic methanotrophs.