中文摘要：

利用PYGV、R2A、NB和Czapek 4种培养基,研究了不同海拔下黑河上游祁连山区土壤细菌群落结构的变化规律.结果表明:可培养细菌数量为4.6×106～37.0×106 CFU·g-1,随海拔升高明显减少;基于16SrRNA基因序列分析共发现了7个门、19个属、26种细菌,其中Agreia pratensis,Mucilaginibacter ximonensis,嗜冷冷杆菌(Cryobacterium psychrophilum)和氧化节杆菌(Arthrobacteroxydans)四种细菌是优势种;嗜冷冷杆菌的相对丰度在高海拔地区明显增加,Agreia pratensis的相对丰度随海拔升高而降低;细菌的多样性随海拔升高呈现出先升高后降低的趋势.冗余分析(RDA)显示,可培养细菌数量与海拔呈显著负相关,细菌的多样性与植被指数和土壤理化性质均存在明显的相关关系,说明可培养细菌数量主要受海拔的影响,而植被和土壤理化性质是影响细菌群落多样性的主要因素.

英文摘要：

The upper reaches of the Heihe River are located in the Qilian Mountains on the eastern edge of the Tibetan Plateau.There are many reports on the hydrology and vegetation of the reaches,but less of them involve the distribution of soil bacterial communities.In this paper,soil samples were collected at different altitudes(2 814-4 130 m above sea level) from the upper reaches of the Heihe River.Cultivable soil bacteria were investigated with PYGV,R2A,NB and Czapek agar mediums.It is found that the number of cultivable bacteria ranges from 4.6 to 37.0(106 CFU·g-1).Population fluctuation of bacteria is significant along with altitudes(P<0.05).From the soil 26 species were isolated by sequencing PCR-amplified 16S rDNA.These species are affiliated with 19 genera belonging to α-Proteobacteria,β-Proteobacteria,γ-Proteobacteria,Actinobacteria,Bacteroides,Firmicutes and Verrucomicrobia.Among them,Agreia pratensis,Mucilaginibacter ximonensis,Cryobacterium psychrophilum and Arthrobacter oxydans are dominant species.The relative abundance of Cryobacterium psychrophilum obviously concentrates at high altitude,but that of Agreia pratensis decreases with altitude.Statistical analysis shows that altitude and vegetation type are the principal environmental factors in the upper reaches of the Heihe River,which affect the distribution of bacterial community.Cultivable number of bacteria has negative correlation with altitude,and the diversity of bacteria increases firstly and then decreases with altitude,which is primarily controlled by plant biomass and cover degree.Besides,the diversity of cultivable bacteria is also correlated with some soil physicochemical properties(e.g.,organic material,total organic carbon,salt and available K).