Termite mounds have recently been confirmed to mitigate approximately half of termite methane (CH₄) emissions, but the aerobic CH₄ oxidising bacteria (methanotrophs) responsible for this consumption have not been resolved. Here, we describe the abundance, composition and CH₄ oxidation kinetics of the methanotroph communities in the mounds of three distinct termite species sampled from Northern Australia. Results from three independent methods employed show that methanotrophs are rare members of microbial communities in termite mounds, with a comparable abundance but distinct composition to those of adjoining soil samples. Across all mounds, the most abundant and prevalent methane monooxygenase sequences were affiliated with upland soil cluster α (USCα), with sequences homologous to Methylocystis and tropical upland soil cluster (TUSC) also detected. The reconstruction of a metagenome-assembled genome of a mound USCα representative highlighted the metabolic capabilities of this group of methanotrophs. The apparent Michaelis–Menten kinetics of CH₄ oxidation in mounds were estimated from in situ reaction rates. Methane affinities of the communities were in the low micromolar range, which is one to two orders of magnitude higher than those of upland soils, but significantly lower than those measured in soils with a large CH₄ source such as landfill cover soils. The rate constant of CH₄ oxidation, as well as the porosity of the mound material, were significantly positively correlated with the abundance of methanotroph communities of termite mounds. We conclude that termite-derived CH₄ emissions have selected for distinct methanotroph communities that are kinetically adapted to elevated CH₄ concentrations. However, factors other than substrate concentration appear to limit methanotroph abundance and hence these bacteria only partially mitigate termite-derived CH₄ emissions. Our results also highlight the predominant role of USCα in an environment with elevated CH₄ concentrations and suggest a higher functional diversity within this group than previously recognised.

最近已证实白蚁丘可以减少大约一半的白蚁甲烷 (CH ₄ ) 排放，但造成这种消耗的需氧 CH ₄氧化细菌（甲烷氧化菌）尚未得到解决。在这里，我们描述了从澳大利亚北部采集的三种不同白蚁物种的土丘中甲烷氧化菌群落的丰度、组成和 CH ₄氧化动力学。采用三种独立方法的结果表明，甲烷氧化菌是白蚁丘微生物群落中的稀有成员，其丰度与邻近土壤样品相当，但组成不同。在所有土丘中，最丰富和最普遍的甲烷单加氧酶序列属于高地土壤簇 α (USCα)，还检测到与甲基囊藻和热带高地土壤簇 (TUSC) 同源的序列。对 USCα 代表的宏基因组组装基因组的重建突出了这组甲烷氧化菌的代谢能力。根据原位反应速率估算了土堆中 CH ₄氧化的表观 Michaelis-Menten 动力学。群落的甲烷亲和力处于低微摩尔范围，比高地土壤的甲烷亲和力高一到两个数量级，但显着低于在垃圾填埋场覆盖土等具有大量CH ₄源的土壤中测量的甲烷亲和力。 CH ₄氧化速率常数以及蚁丘材料的孔隙率与白蚁蚁丘甲烷氧化菌群落的丰度显着正相关。 我们得出的结论是，白蚁衍生的 CH ₄排放选择了不同的甲烷氧化菌群落，这些群落在动力学上适应了升高的 CH ₄浓度。然而，底物浓度以外的因素似乎限制了甲烷氧化菌丰度，因此这些细菌只能部分减轻白蚁衍生的 CH ₄排放。我们的结果还强调了 USCα 在 CH ₄浓度升高的环境中的主要作用，并表明该组内的功能多样性比以前认识到的更高。