水稻土是非常复杂又典型的生态系统, 分析淹水培养过程中水稻土细菌的丰度和群落结构变化规律, 可以客观反映水稻土中细菌群落结构信息, 为深入探讨水稻土细菌微生物对稻田的影响和在生态系统中的作用(营养元素转换、重金属还原与抑制甲烷生成过程等)提供实验基础与理论依据。作者采用淹水非种植水稻土微环境模式系统, 提取水稻土淹水培养1 h和1、5、10、20、30、40、60 d后的微生物总DNA, 利用Real-time PCR和PCR-DGGE (denaturing gradient gel electrophoresis)技术检测了淹水培养过程中细菌丰度与群落结构的变化。结果表明: 淹水水稻土中细菌的丰度在1 d时最大, 并在40 d到达第二个峰值, 说明淹水过程改变了细菌的丰度。基于16S rRNA基因V3区的DGGE图谱分析显示, 淹水过程中细菌的群落结构发生了演替性变化: r-策略生存的细菌仅存在于淹水初期; k-策略生存的细菌存在于淹水后期; r-和k-策略共生存的细菌存在于整个淹水过程中, 淹水后期k-策略的细菌占据优势。淹水培养过程中优势种群多样性指数大体呈现先上升后减小的趋势。主成分分析(PCA)将淹水处理过程分成几类不同的生境, 反映出中、后期细菌群落结构较为稳定; 测序结果表明, 32个优势条带所代表的细菌分别属于厚壁菌门、绿弯菌门、拟杆菌门、变形菌门和酸杆菌门, 且与来自不同地域的水稻土、其他类型土壤、活性污泥以及湖泊沉积物等生态系统的细菌关系密切。

Paddy soil is a complex and typical ecosystem. Investigating changes to paddy soil bacterial communities during flooding can provide a theoretical basis for further exploring bacterial effects on and functions in ecosystems, e.g. nutrient transformations, the suppression of methanogenesis and bioremediation of heavy metal pollution. In this study, bacterial genomic DNA was analyzed from 8 paddy soil samples with flooding periods of 1 h, 1 d, 5 d, 10 d, 20 d, 30 d, 40 d and 60 d, respectively. 16S rRNA gene-based real-time PCR and PCR-DGGE (denaturing gradient gel electrophoresis) were used to study abundance and community structure during different flooding periods. The highest bacterial abundance was observed at 1 d with the second highest value at 40 d, indicating that bacterial abundance fluctuated over the flooding period. Succession of bacterial community structure was observed along the entire flooding period: r-strategists were only present in the early flooding stage; k-strategists emerged and were dominant in the late flooding stage; r-k-strategists symbiotic organisms were present in the entire flooding period. The diversity of the bacterial community during the flooding period rose initially and then tended to drop as succession took place. Principal Components Analysis based on digitized DGGE patterns indicated that the changes to bacterial community structure slowed during the mid- to late flooding stages. Sequencing results showed that Firmicutes, Chloroflexi, Bacteroidetes, Proteobacteria and Acidobacteria, which have close phylogenetic relationships with the groups from paddy soils and other soils of different regions, activated sludge systems and lake sediments, were the dominant habitants of the study site.