Does increased methane concentration change in structure and diversity of soil prokaryotes along artificial pH gradient?

Methane is a greenhouse gas whose global warming potential is 25 times higher than that of carbon dioxide. Oxidation of methane by methanotrophs in alpine wet meadow is a major biological sink for atmospheric methane, which accounts for up to 10% of the total methane oxidation in the atmosphere. Recent studies indicated both unequal spatial distribution of soil prokaryotes including methanothrops at global scale as well as effect of soil properties on distribution and activity of soil microbiota at local scale. However, response pattern of soil microbiota at taxonomic level to artificial shift of soil properties under elevated methane addition remains still unclear. To do this, we established experiment consisting from glass bottles with soils treated by various pH. After one month of incubation, 300 ml of methane in concentration of 10 ppm was added. Our study reveals different response pattern of soil prokaryotic communities to artificial pH gradient under elevated methane concentration. Methane addition increased microbial alpha diversity measured by Chao index. We suggest that structure of soil prokaryotic community based on UniFrac distance is strongly affected by changes in relative abundance of Chloroflexi and Gemmatimonadetes along artificial pH gradient. Our analysis of phylogenetic structure showed that disturbances such as change of original pH promotes importance of deterministic processes. Relative abundance of Chloroflexi indicated decreasing in soils with acidic pH, while relative abundance of Gemmatimonadetes showed higher abundance in soils with alkaline pH. Soils treated by acidic pH showed lower relative abundance of Alphaproteobacteria than soils with alkaline pH showing higher relative abundance of Alphaproteobacteria. Artificial pH affects methane oxidation rates through stimulation/suppression of bacterial growth or activity as well as substantial shifts in the methanotroph community structure.