Stable-isotopic and metagenomic analyses reveal metabolic and microbial link of aerobic methane oxidation coupled to denitrification at different O 2 levels

• Published in: The Science of the total environment 2021-04, Vol.764, p.142901
• Main Authors: Ma, Ruo-Chan, Chu, Yi-Xuan, Wang, Jing, Wang, Cheng, Leigh, Mary Beth, Chen, Yin, He, Ruo
• Format: Article
• Language: English
• Subjects: Denitrification; Ecosystem; Metagenomics; Methane; Oxidation-Reduction
• ISSN: 1879-1026
• DOI: 10.1016/j.scitotenv.2020.142901

Aerobic methane (CH ) oxidation coupled to denitrification (AME-D) can not only mitigate CH emission into the atmosphere, but also potentially alleviate nitrogen pollution in surface waters and engineered ecosystems, and it has attracted substantial research interest. O concentration plays a key role in AME-D, yet little is understood about how it impacts microbial interactions. Here, we applied isotopically labeled K NO and CH and metagenomic analyses to investigate the metabolic and microbial link of AME-D at different O levels. Among the four experimental O levels of 21%,10%, 5% and 2.5% and a CH concentration of 8% (i.e., the O /CH ratios of 2.62, 1.26, 0.63 and 0.31), the highest NO -N removal occurred in the AME-D system incubated at the O concentration of 10%. Methanol and acetate may serve as the trophic linkage between aerobic methanotrophs and denitrifers in the AME-D systems. Methylotrophs including Methylophilus, Methylovorus, Methyloversatilis and Methylotenera were abundant under the O -sufficient condition with the O concentration of 21%, while denitrifiers such as Azoarcus, Thauera and Thiobacillus dominated in the O -limited environment with the O concentration of 10%. The competition of denitrifiers and methylotrophs in the AME-D system for CH -derived carbon, such as methanol and acetate, might be influenced by chemotactic responses. More methane-derived carbon flowed into methylotrophs under the O -sufficient condition, while more methane-derived carbon was used for denitrification in the O -limited environment. These findings can aid in evaluating the distribution and contribution of AME-D and in developing strategies for mitigating CH emission and nitrogen pollution in natural and engineered ecosystems.