Abstract
Methanotrophic bacteria are able to use methane (CH4) as a sole carbon and energy source. Photochemical oxidation of methane takes place in the stratosphere, whereas in the troposphere, this process is carried out by methanotrophic bacteria. On the one hand, it is known that the efficiency of biological CH4 oxidation is dependent on the mode of land use but, on the other hand, the knowledge of this impact on methanotrophic activity (MTA) is still limited. Thus, the aim of the study was to determine the CH4 oxidation ability of methanotrophic bacteria inhabiting selected arable and no-tillage soils from the Lublin region (Albic Luvisol, Brunic Arenosol, Haplic Chernozem, Calcaric Cambisol) and to identify bacteria involved in this process. MTA was determined based on incubation of soils in air with addition of methane at the concentrations of 0.002, 0.5, 1, 5, and 10%. The experiment was conducted in a temperature range of 10–30 °C. Methanotrophs in soils were identified by next-generation sequencing (NGS). MTA was confirmed in all investigated soils (in the entire range of the tested methane concentrations and temperatures, except for the arable Albic Luvisol). Importantly, the MTA values in the no-tillage soil were nearly two-fold higher than in the cultivated soils. Statistical analysis indicated a significant influence of land use, type of soil, temperature, and especially methane concentration (p < 0.05) on MTA. Metagenomic analysis confirmed the presence of methanotrophs from the genus Methylocystis (Alphaproteobacteria) in the studied soils (except for the arable Albic Luvisol). Our results also proved the ability of methanotrophic bacteria to oxidize methane although they constituted only up to 0.1% of the total bacterial community.
Highlights
Methane (CH4) is the second of the most important greenhouse gases after carbon dioxide (CO2)
The aim of our study is to find the answers to the following questions: (1) How does methanotrophic activity (MTA) change across types of soil representative for Poland? (2) How does the land use mode modify MTA? (3) What is the response of methanotrophic bacteria to an increase in the CH4 concentration in the atmosphere? (4) Is this response similar in all soil types? (5) Which methanotrophs are involved in CH4 oxidation in Polish mineral soils?
Among the types of soils investigated in this study, the highest methane oxidation potential was found in Haplic Chernozem
Summary
Methane (CH4) is the second of the most important greenhouse gases after carbon dioxide (CO2). Based on carbon assimilation pathways, phylogeny, chemotaxonomy, and internal membrane structure, methanotrophs have been divided into two types Both methanotrophic type I and type II typically inhabit aerobic interfaces between anoxic and oxic zones of methanogenic environments such as natural wetlands or rice paddies and reduce the potential of CH4 flux to the atmosphere by up to 90% [11]. Type II is characterized by low-capacity MTA (able to oxidize CH4 at a mixing ratio below 40 ppm); its representatives are prevalent mostly in CH4-poor but oxygen-rich environments. This division suggests that different methanotrophs can be involved in CH4 oxidation in wetlands and lowland soils
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