Ammonium and lanthanum impact methane oxidation and methanotrophic communities in agricultural soils.

An ever-increasing amount of research is being done on the stability and recovery of soil methane-oxidizing bacteria since it is one of the fundamental processes controlling the amount of methane in the atmosphere. Mineral fertilizers may alter the methane oxidation processes in agricultural soils when they are introduced. Although ammonium (NH₄⁺) is believed to have a significant impact on the aerobic methane oxidation activity in soils, there is still little data on how it reacts with lanthanum (La). The recent identification of a novel class of lanthanum-containing enzymes in methanotrophic bacteria may be the foundation for controlling the function of the soil "methane filter" and related microbiota. In the current study, microcosms with agricultural soddy-podzolic soils were created. These microcosms had 20% CH4 in the gas phase, varying amounts of NH₄+ (100 and 200 µg/g) and La (5, 10, and 20 µg/g) in the soil. Using GC analysis and high-performance 16S rRNA sequencing, the methane oxidation potential and composition of soil bacterial communities were studied over a month of incubation. A negative impact of NH₄⁺ on the oxidation of methane was observed, whereas La had a somewhat beneficial effect. Ammonium had an impact on the composition of methanotrophs, and a significant shift was observed at all La levels. Proteobacteria made up a larger share of the soil microbial community, and Gammaproteobacteria dominated the methanotrophic populations. Methylobacter, a methanotroph, and Methylotenera, an obligatory methylotroph, were the two absolute dominants in the La amended variants. The findings here reported could help evaluate how lanthanum regulates methanotrophic communities in agricultural soils and lead to the creation of new strategies for controlling the methane cycling in soils.