School of Science, Technology, Engineering and Math, Diné College, Tsaile, Arizona, USA.
Planetary Science Institutegrid.423138.f, Tucson, Arizona, USA.
Microbiol Spectr. 2022 Aug 31;10(4):e0156621. doi: 10.1128/spectrum.01566-21. Epub 2022 Aug 9.
Methane oxidizing microorganisms (methanotrophs) are ubiquitous in the environment and represent a major sink for the greenhouse gas methane (CH). Recent studies have demonstrated methanotrophs are abundant and contribute to CH dynamics in caves. However, very little is known about what controls the distribution and abundance of methanotrophs in subterranean ecosystems. Here, we report a survey of soils collected from > 20 caves in North America to elucidate the factors shaping cave methanotroph communities. Using 16S rRNA sequencing, we recovered methanotrophs from nearly all (98%) of the samples, including cave sites where CH concentrations were at or below detection limits (≤0.3 ppmv). We identified a core methanotroph community among caves comprised of high-affinity methanotrophs. Although associated with local-scale mineralogy, methanotroph composition did not systematically vary between the entrances and interior of caves, where CH concentrations varied. We also observed methanotrophs are able to disperse readily between cave systems showing these organisms have low barriers to dispersal. Lastly, the relative abundance of methanotrophs was positively correlated with cave-air CH concentrations, suggesting these microorganisms contribute to CH flux in subterranean ecosystems. Recent observations have shown the atmospheric greenhouse gas methane (CH) is consumed by microorganisms (methanotrophs) in caves at rates comparable to CH oxidation in surface soils. Caves are abundant in karst landscapes that comprise 14% of Earth's land surface area, and therefore may represent a potentially important, but overlooked, CH sink. We sampled cave soils to gain a better understand the community composition and structure of cave methanotrophs. Our results show the members of the USC- clade are dominant in cave communities and can easily disperse through the environment, methanotroph relative abundance was correlated with local scale mineralogy of soils, and the relative abundance of methanotrophs was positively correlated with CH concentrations in cave air.
甲烷氧化微生物（甲烷营养菌）在环境中无处不在，是温室气体甲烷（CH）的主要汇。最近的研究表明，甲烷营养菌在洞穴中丰富且对 CH 动态有贡献。然而，对于控制地下生态系统中甲烷营养菌的分布和丰度的因素知之甚少。在这里，我们报告了对来自北美的 20 多个洞穴的土壤样本的调查，以阐明塑造洞穴甲烷营养菌群落的因素。通过 16S rRNA 测序，我们从几乎所有（98%）的样本中都回收了甲烷营养菌，包括 CH 浓度处于或低于检测限（≤0.3ppmV）的洞穴。我们在洞穴中确定了一个核心甲烷营养菌群落，由高亲和力甲烷营养菌组成。尽管与局部尺度的矿物学有关，但甲烷营养菌的组成并没有在洞穴入口和内部之间系统地变化，而 CH 浓度在洞穴入口和内部之间变化。我们还观察到甲烷营养菌能够在洞穴系统之间迅速扩散，表明这些生物体对扩散的障碍较低。最后，甲烷营养菌的相对丰度与洞穴空气 CH 浓度呈正相关，表明这些微生物对地下生态系统中的 CH 通量有贡献。最近的观察表明，大气温室气体甲烷（CH）在洞穴中被微生物（甲烷营养菌）以与地表土壤中 CH 氧化相当的速率消耗。洞穴在由地球表面面积的 14%组成的喀斯特景观中大量存在，因此可能代表一个潜在重要但被忽视的 CH 汇。我们对洞穴土壤进行了采样，以更好地了解洞穴甲烷营养菌的群落组成和结构。我们的结果表明，USC- 分支的成员在洞穴群落中占优势，并且可以很容易地通过环境扩散，甲烷营养菌的相对丰度与土壤的局部尺度矿物学有关，并且甲烷营养菌的相对丰度与洞穴空气中的 CH 浓度呈正相关。
