Methanol oxidation by temperate soils and environmental determinants of associated methylotrophs

Abstract

The role of soil methylotrophs in methanol exchange with the atmosphere has been widely overlooked. Methanol can be derived from plant polymers and be consumed by soil microbial communities. In the current study, methanol-utilizing methylotrophs of 14 aerated soils were examined to resolve their comparative diversities and capacities to utilize ambient concentrations of methanol. Abundances of cultivable methylotrophs ranged from 10 ⁶-10 ⁸gsoilDW ⁻¹. Methanol dissimilation was measured based on conversion of supplemented 14C-methanol, and occurred at concentrations down to 0.002 μmol methanol gsoilDW ⁻¹. Tested soils exhibited specific affinities to methanol (a ⁰ s=0 ⁻¹) that were similar to those of other environments suggesting that methylotrophs with similar affinities were present. Two deep-branching alphaproteobacterial genotypes of mch responded to the addition of ambient concentrations of methanol (≤0.6 μmol methanol gsoilDW ⁻¹) in one of these soils. Methylotroph community structures were assessed by amplicon pyrosequencing of genes of mono carbon metabolism (mxaF, mch and fae). Alphaproteobacteria-affiliated genotypes were predominant in all investigated soils, and the occurrence of novel genotypes indicated a hitherto unveiled diversity of methylotrophs. Correlations between vegetation type, soil pH and methylotroph community structure suggested that plant-methylotroph interactions were determinative for soil methylotrophs.