Distribution and functions of methanotrophs in the sediments of Aha Lake Reservoir,Guizhou Province

Abstract:

Methanotrophs can utilize methane as the only carbon source and energy, and they can survive and participate in material circulation and energy flow in ecosystems. 【Objective】 To unveil the structure and functions of methanotrophs community in the sediments from the Aha Lake Reservoir (referred to as the Reservoir), a typical karst lake reservoir in Guiyang City, Guizhou Province. 【Methods】 We used metagenomics to analyze the sediments collected from the edge and the center of the Reservoir. 【Results】 The dominant aerobic methanotrophs were Methylobacter (0.37%) and Methylomonas (0.12%), and the dominant anaerobic methanotrophs were Candidatus_Methylomirabilis (0.12%), being NC10 denitrifying anaerobic methanotrophs. The gene pmoA encoding particulate methane monooxygenase of aerobic methanotrophs had the relative abundance of 6.16×10⁷ copies/g and the 16S rRNA gene had the relative abundance of 2.84×10⁷ copies/g in denitrifying anaerobic methanotrophs. The diversity of four metabolic functional genes followed a trend of nitrogen metabolism>carbon metabolism>sulfur metabolism>methane metabolism. Kyoto encyclopedia of genes and genomes (KEGG) annotation revealed six functions and 18 complete pathways involving carbon (including methane), nitrogen, and sulfur metabolism. The results of principal coordinate analysis (PCoA) showed huge discrepancies in the distribution and functions of methanotrophs between sediments from the edge and the center of the Reservoir. Moreover, redox potential, conductivity, and sulfate were primary environmental factors affecting methanotroph distribution. 【Conclusion】 Type I aerobic methanotrophs dominated the Reservoir with abundant metabolic pathways. Types I and II methanotrophs exhibited huge discrepancies in terms of their adaptability to O₂. All these fundings are expected to provide theoretical support for lake water environment conservation and microbial utilizationation.