喀斯特原生土壤与退化生态系统土壤细菌群落结构

运用PCR-RFLP技术，对桂西北喀斯特原生土壤和退化生态系统土壤细菌16S rDNA基因多样性及系统发育关系进行了研究.结果表明：原生土壤比退化生态系统土壤具有更丰富的16S rDNA基因型和更高的多样性指数，两样地共有的基因型仅有2个.从每种基因型中随机选择一个克隆子作为代表进行测序分析，所有序列与GenBank 数据库中序列的同源性为87%～100%，且两样地中均有超过一半的基因型序列与数据库中已知序列同源性低于97%，属于分类在“种”地位上的新发现细菌;通过系统发育研究将两样地的细菌分为10大类群，两样地共同拥有5大类群，但两样地的细菌优势类群明显不同，原生土壤为Proteobacteria，含39种基因型，占总克隆子数的58.0%，退化生态系统土壤为Acidobacteria和Proteobacteria，分别含19种和15种基因型，占总克隆子数的32.5%和30.5%;与原生土壤细菌类群相比，退化生态系统土壤Proteobacteria类群明显减少，Acidobacteria类群明显增加.土壤理化性质及土壤环境因素的差异是引起两类型土壤细菌多样性差异的原因.

Soil bacterial community structure in primeval forest and degraded ecosystem in Karst region.

By using PCR-RFLP, this paper studied the 16S rDNA gene diversity and phylogenesis of soil bacteria in primeval forest and degraded ecosystem in Karst region of Northwest Guangxi. More genotypes and higher diversity index were observed in the soil of primeval forest than in that of degraded ecosystem, and only two common genotypes were observed in the two soils. A clone from each genotype was randomly selected as representative for sequencing. The obtained 16S rDNA gene sequences had a similarity of 87%〖KG-*2〗-〖KG-*7〗100% with those in the GenBank (www.ncbi.nlm.nih.gov), and more than half of them had a similarity lower than 97%, being of new species. Based on phylogenetic analysis, the bacteria in the two soils were classified into 10 groups, with 5 groups in common. The dominant bacterial groups in the two soils differed obviously. In primeval forest soil, the dominant group was Proteobacteria, which had 39 genotypes, occupying 580% of all the clones; while in the soil of degraded ecosystem, the dominant groups were Acidobacteria and Proteobacteria, which had 19 and 15 genotypes, occupying 325% and 305% of all the clones, respectively. In the soil of degraded ecosystem, Proteobacteria group decreased while Acidobacteria group increased markedly, compared with those in primeval forest soil. Soil physical and chemical properties and environmental factors should be responsible for the difference of soil bacterial community between the two soils.