青藏高原淡水湖普莫雍错和盐水湖阿翁错湖底沉积物中细菌群落的垂直分布

【目的】湖泊沉积物中存储着大量独特的微生物,这些微生物在湖泊生态系统生物地球化学循环中扮演着非常重要的角色。然而,很少有研究报道微生物群落在湖泊沉积物中的垂直分布。本文比较研究青藏高原淡水湖普莫雍错和盐水湖阿翁错沉积物在不同深度下细菌的丰度和群落结构。【方法】利用定量PCR(q PCR)和变性梯度凝胶电泳(DGGE)技术分别测定细菌群落的丰度与群落结构。【结果】定量PCR结果显示,湖泊沉积物中细菌丰度均随深度增加而降低,盐水湖阿翁错和淡水湖普莫雍错的细菌丰度分别从1011数量级降到108数量级,从1012数量级降到1010数量级。在相对应的沉积物层,淡水湖沉积物的细菌丰度比盐水湖高1-2个数量级。变性梯度凝胶电泳(DGGE)指纹图谱的分析表明,淡水湖沉积物细菌群落的DGGE条带数(丰富度)显著高于盐水湖(P=0.014);淡水与盐水湖泊沉积物细菌群落结构明显不同,同时在同一湖泊沉积物中上层(0-6 cm)和下层(7-20 cm)细菌群落结构也呈明显分异。系统发育分析表明,盐水湖阿翁错沉积物特有菌门为Gamma-变形菌、拟杆菌门、蓝细菌和栖热菌门,而淡水湖普莫雍错沉积物中特有菌门为Delta-和Beta-变形菌、酸杆菌和绿弯菌门。【结论】青藏高原淡水与盐水湖泊沉积物细菌丰度与群落结构具有明显的差异;同时,细菌群落结构在沉积物的不同深度也表现出差异。这些结果可为进一步阐明青藏高原湖泊生态系统中微生物对气候环境变化的响应提供科学依据。

Vertical distribution of bacterial community in sediments of freshwater lake Puma Yumco and saline lake AWongco on the Tibetan Plateau

Objective] Lake sediments store huge amount of specific microorganisms that greatly contribute to biogeochemical processes in lake ecosystems. However, there is little information about the vertical distribution of microbial community along lake sediment profile. In this study, we investigated the abundance and structure of pristine sediment bacterial communities along a depth gradient (0?20 cm) in a freshwater lake Puma Yumco and a saline lake AWongco on the Tibetan Plateau. Methods] Real-time quantitative PCR (qPCR) and denaturant gradient gel electrophoresis (DGGE) were used to determine the bacterial abundance and community structure, respectively. Results] Bacterial abundance consistently decreased along vertical depth in the two lake sediments and the abundance decreased from 1012 to 1010 in freshwater lake and from 1011 to 108 in saline lake, respectively. Bacterial abundances in freshwater lake were one order of magnitude higher than those in saline lake at each vertical depth. DGGE analysis showed that the bacterial richness was significantly higher (p=0.014) in freshwater lake than saline lake sediments; the bacterial community composition was clearly different between these two lake sediments, and the communities differed between upper (0?7 cm) and lower (7?20 cm) depths. Phylogenetic analysis showed that Gamma-proteobacteria, Bacteroidetes, Deinococcus-Thermus and Cyanobacteria were present in saline sediments while Delta- and Beta-proteobactria, Acidobacteria and Chloroflexi were only detected in freshwater sediment. Conclusion] These results indicated that bacterial abundance and community structure differed dramatically between freshwater lake and saline lake sediments, and the microbial community composition also differed along the depth of sediments. Our results could provide the scientific base on how microbes in lake ecosystems respond to climate change on the Tibetan Plateau.