Abstract：
Karst caves are potential sinks of atmospheric methane due to microbial consumption. However, knowledge gaps on methanogens (methane producing microorganisms) and their interaction with methane-oxidizing bacteria (MOB) hinder our further understanding about methane dynamics in karst caves. Here we reported methanogenic community composition and their interaction with MOBs in the Heshang Cave to comprehensively understand methane cycling in subsurface biosphere. MOBs in karst cave were dominated by high-affinity MOB, upland soil cluster (USC), with USCγ pmoA gene abundance within the range of 1.34 × 104 to 1.8 × 107 copies·g-1 DW. In contrast, methanogens were dominated by Methanoregula and cluster ZC-I. The mcrA numbers were 7.21 × 103 to 8.31 × 104 copies·g-1 DW, 1-3 orders of magnitude lower than those of MOB. The inter-domain network analysis indicated that MOBs and methanogens cooperated more in the interior of the cave. Despite of the higher number of methanogenic nodes in the network, MOB dominated the keystone taxa, suggesting a leading functional role of MOB. MOB in caves showed a comparable with or higher potential methane oxidizing rate (PMOR, 0.63 ng CH4·g-1 DW·h-1 in sediment versus 11.02 ng CH4·g-1 DW·h-1 in weathered rock) than those in soils, whereas methane produced by methanogens was undetected. Collectively, high absolute abundances of MOB, high PMORs, the dominance of methanotrophic keystone taxa in the inter-domain network confirmed the superiority of MOBs over methanogens in the oligotrophic karst cave, mounting new evidence on caves as an important methane sink in terms of the interaction between methanogens and MOBs.
摘要：
由于微生物的消耗，岩溶洞穴是大气甲烷的潜在汇。然而,关于产甲烷菌（产甲烷微生物）及其与甲烷氧化细菌（MOB）的相互作用的知识空白阻碍了我们对岩溶洞穴中甲烷动力学的进一步了解。在这里，我们报道了和尚洞中产甲烷菌群落组成及其与MOB的相互作用，以全面了解地下生物圈中的甲烷循环。岩溶洞穴中MOB以高亲和力MOB为主，旱地土壤集群(USC)，USCγpmoA基因丰度在1.34×104至1.8×107拷贝·g-1DW范围内。相比之下,产甲烷菌以甲烷调节菌和ZC-I簇为主。mcrA编号为7.21×103至8.31×104拷贝·g-1DW，比MOB低1-3个数量级。域间网络分析表明，MOBs和产甲烷菌在洞穴内部更多地合作。尽管网络中产甲烷节点的数量较多，暴民统治了梯形分类群，表明MOB的主导作用。洞穴中的MOB显示出相当或更高的潜在甲烷氧化率(PMOR，沉积物中的0.63ngCH4·g-1DW·h-1与风化岩石中的11.02ngCH4·g-1DW·h-1）比土壤中的高，而产甲烷菌产生的甲烷未被检测到。总的来说，暴民的绝对丰度很高，高PMors，甲烷营养梯形分类群在域间网络中的优势证实了MOB优于贫营养溶洞中的产甲烷菌，就产甲烷菌和MOBs之间的相互作用而言，洞穴是重要的甲烷汇。
