摘要:湖泊生态系统排放的甲烷（CH₄）大部分来自湖滨湿地，好氧甲烷氧化细菌（methane-oxidizing bacteria，MOB）在减轻CH₄从湖泊系统向大气的排放中起着至关重要的作用。湖滨湿地好氧MOB群落分布及其影响因素尚不清楚。采用qPCR、末端限制性片段长度多态性（T-RFLP）等方法，分四季对贵州草海湖滨湿地宽敞水域至落干区沉积物中好氧MOB群落组成和数量进行了研究。草海湖滨湿地沉积中甲烷氧化单加氧酶功能基因（pomA）丰度较高，在1.78×10⁷-2.73×10⁸拷贝数/g干沉积物之间，好氧MOB由I型（Methylococcus and Methylobacter）和II型（Methylosinus）组成，I型主要分布在宽敞水域（长期淹水区），而干湿过渡区和偶尔积水区主要为II型，呈现出明显的空间变化，推测湖滨湿地长期淹水区甲烷的氧化由I型主导，而相对干旱的区域II型主导，而这种差异可能是导致湖滨湿地甲烷排放高度异质性的一个重要因素。研究结果对揭示湖滨湿地甲烷排放时空异质性的微生物生态机制奠定了基础。



Abstract:Methane (CH₄) is the second largest greenhouse gas in the atmosphere after CO₂, contributing 30%-40% of the global greenhouse effect. CH₄ in the atmosphere mainly comes from human activities and natural ecosystem release. In lake ecosystems, a major proportion of CH₄ emissions originates from the littoral wetland, which has a great deal of spatial variability in hydrology, sediment quality and vegetation. Methanotrophs play a crucial role in mitigating CH₄ emissions from lake systems to the atmosphere. However, the distribution of the aerobic methane-oxidizing bacteria (MOB) community in the littoral wetland and their driving factors are less understood. In this article, we investigated the MOB communities in habitats ranging from an open water area (permanently flooded) to an occasionally flooded area in the littoral wetland of Caohai in Guizhou in four different seasons. The MOB communities were characterized by quantitative PCR, terminal restriction fragment length polymorphism (T-RFLP), and sequencing of pmoA genes encoding the α subunit of the particulate methane monooxygenase. The abundance and structure of the sediment methanotrophic community showed a remarkable spatial variation. The littoral sediment methanotrophic communities were composed of Methylococcus and Methylobacter (type I methanotrophs) and Methylosinus (type II methanotrophs). Type I methanotrophs were most abundant in the permanently flooded area whereas type II methanotrophs were most abundant in the dry-wet transition zone and the occasionally flooded area. An explanation for this distribution pattern is that type I MOB usually have a lower affinity for CH₄ than type II MOB, therefore, type I MOB have a strong competitive advantage in places with high CH₄ levels. In addition, type II MOB are considered to be K-strategists and have a better ability to endure drought than type I MOB. This suggests that different types of methanotrophs may participate in CH₄ oxidation under different water levels in the littoral wetland. Our study gives an in-depth insight into the spatio-temporal heterogeneity of MOB community composition in the littoral wetland of Yunnan-Guizhou Plateau lake. The hydrological conditions are important factors determining the spatio-temporal heterogeneity of MOB communities in littoral wetlands that directly, or indirectly affect the spatio-temporal distribution of MOB communities through regulating physicochemical conditions and plant communities in sediments. However, further studies are still needed to understand the role of type I and type Ⅱ MOB in CH₄ oxidation in the littoral wetland community and to clarify the effect of sediment pH and plant community on the littoral wetland MOB community distribution regulation mechanisms.





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