Aerobic methanol-oxidizing bacteria in soil.

Methanol is an atmospheric compound that is primarily released from plant polymers and impacts ozone formation. The global methanol emission rate from terrestrial ecosystems is of the same order of magnitude (4.9 x 10(12) mol year(-1)) as that of methane (10 x 10(12) mol year(-1)). The major proportion of the annual plant-released methanol does not enter the atmosphere, but may be reoxidized by biological methanol oxidation, which is catalyzed by methanol-oxidizing prokaryotes. Fifty-six aerobic methanol-oxidizing species have been isolated from soils. These methylotrophs belong to the Alpha-, Beta-, and Gammaproteobacteria, Verrucomicrobia, Firmicutes, and Actinobacteria. Their ecological niches are determined by oxygen and methanol concentration, temperature, pH, the capability to utilize nitrate as an electron acceptor, and the spectrum of nitrogen sources and utilizable multicarbon substrates. Recently discovered interactions with eukaryotes indicate that their ecological niches may not solely be defined by physicochemical parameters. Nonetheless, there are still gaps in knowledge; based on global methanol budgets, methanol oxidation in soil is important, but has not been addressed adequately by biogeochemical studies. Ratios of above-ground and soil-internal methanol oxidation are not known. The contribution to methanol-oxidation by aerobic and anaerobic methylotrophs in situ also needs further research.