中国和美国原始土壤中非高温泉古菌的发现和鉴定

近年来在非极端环境中已经发现有古菌(Archaea)的存在, 但在中国原始土壤中还未见报道。本研究的目的是调查古菌是否存在于两个分别取自中国新疆和广西的土壤及两个美国亚利桑那州南部地区的土壤中。我们分别构建了这四个原始土壤的古菌16S rDNA文库并对28个克隆的16S rDNA进行了鉴定。所有这些16S rDNA的序列都归类于古菌的泉古菌门(Crenarchaeota)。进化树分析表明, 这些泉古菌的16S rDNA属于非高温陆地环境中的泉古菌种群, 明显区别于海洋和淡水地带的泉古菌种群。这个泉古菌种群又有两个分支, 这两个分支在16S rDNA序列上和G C含量上有明显的区别。本研究在两个中国和两个美国原始土壤中鉴定了非高温泉古菌的存在, 由此证明泉古菌的存在范围不只局限于高温等极端环境。另外, 美国原始土壤中的泉古菌只属于一个进化分支, 这说明非高温泉古菌种群的类型和土壤的地理位置及土壤特性有关。

Identification of similar non-thermophilic Crenarchaeota in four Chinese and American pristine soils

Archaea have been discovered in non-extreme environments recently but not in Chinese pristine soils so far. This study was conducted to assess the presence of Archaea in two Asian pristine soils from Xin-jiang and Guangxi of China and in two North American soils from southern Arizona region of the United States. Four 16S rDNA clone libraries were generated and 16S rDNAs related to 28 Crenarchaeota were identified in all four soils. All of the 16S rDNA sequences grouped closely with non-thermophilic terrestrial Crenarchaeotae, which is distinct from marine and freshwater crenarchaeotal clusters. Phylogenetic analysis indicated that the recovered 28 crenarchaeotal 16S rDNA sequences belong to two distinct clades that can be distinguished on the basis of either 16S rDNA sequence or G C content. Our results demonstrate the pres-ence of non-thermophilic Crenarchaeota in two Chinese and two American pristine soils for the first time in these regions, indicating that the range of these organisms is not restricted to extreme conditions. In addition, Clade 2 contains clones only from the American soils, indicating that the geographic locations and soil char-acteristics may influence the types of terrestrial crenarchaeotal populations.