水稻土铁还原细菌丰度及群落结构对淹水时间的响应

发布时间：2018-08-15 16:04

【摘要】：Fe(Ⅲ)是厌氧土壤中最丰富的电子受体,铁的氧化和还原过程对碳、氮元素循环,微量营养元素的移动,尤其是有机和无机污染物的降解、转化与固定过程有着强烈的影响。水稻土是非常复杂又典型的生态系统,分析水稻土铁还原细菌丰度和群落结构对淹水培养过程的响应,对深入探讨其铁还原、营养元素转换、抑制甲烷生成及生物修复过程具有重要意义。本文采用Real-time PCR、PCR-DGGE以及文库构建手段,分析了淹水非种植水稻土中细菌及其地杆菌、梭菌、芽孢杆菌、假单胞菌和厌氧粘细菌等典型铁还原菌的丰度和群落结构对淹水时间的响应特征及其与Fe(Ⅲ)还原变化的关系,为进一步明确微生物在异化铁还原及其他生态过程中的作用提供理论依据。获得了以下主要结果:(1)供试水稻土在淹水培养过程中,Fe(Ⅱ)含量在前期(1 h-10 d)迅速增加,而之后趋于稳定;最大还原潜势为5.929 mg/g,最大反应速率为0.989 mg/(g.d),最大反应速率对应的时间(TVmax)为2.853 d。(2)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,淹水过程改变了细菌的丰度。基于16S rDNA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。PCA分析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。(3)对5种典型铁还原细菌的丰度分析表明,整个淹水过程中,芽孢杆菌丰度最高,占绝对优势,假单胞菌丰度最低。在淹水初期,梭菌和芽孢杆菌丰度都快速上升并在1 d达到最大值,而地杆菌、假单胞菌和厌氧粘细菌在1 d时丰度最小,之后呈现上升趋势,分别在40 d、30 d和60 d达到最大。由此推测芽孢杆菌对铁还原过程的贡献最大,假单胞菌的最小。淹水初期,芽孢杆菌和梭菌的贡献较大,而后期对铁还原过程贡献大的是地杆菌、厌氧粘细菌和假单胞菌。(4)对5种典型铁还原细菌的群落结构分析表明,淹水过程中群落结构发生了演替性变化。多样性分析表明,淹水过程中不同细菌的Shannon指数H'变化明显,其中芽孢杆菌的变化最大,从1 h的1.674,到40 d达到最大,为4.129。根据淹水时间的PCA分析显示,总体上讲,与细菌的结果类似,5种铁还原菌也被分成不同的生境,且培养后期均形成了独立的生境,也表明淹水后期群落结构变化趋于稳定。(5)基于DGGE优势条带和克隆文库序列的系统发育分析表明,供试土壤中5种铁还原菌的生态分布广泛,且能与多种具有污染物降解和重金属还原等的微生物聚在一起。(6)CCA分析显示,淹水过程中水稻土的Fe(Ⅱ)浓度、pH值、5种铁还原菌的丰度和香农指数对生境相似度都有贡献。综上所述,细菌及其5种铁还原细菌的丰度和群落结构对淹水时间产生了各自的响应;铁还原菌对水稻土的铁还原过程作出了贡献,推测芽孢杆菌对整个淹水过程的铁还原贡献最大,淹水后期地杆菌和厌氧粘细菌也作出了重要贡献。
[Abstract]:Fe(III) is the most abundant electron acceptor in anaerobic soils. The oxidation and reduction of iron have a strong influence on the cycling of carbon and nitrogen, the movement of micronutrients, especially the degradation, transformation and fixation of organic and inorganic pollutants. Paddy soils are very complex and typical ecosystems. The abundance of iron-reducing bacteria in paddy soils is analyzed. The response of the community structure to the submerged culture process is of great significance to the further study of iron reduction, nutrient transformation, inhibition of methane production and bioremediation. In this paper, Real-time PCR, PCR-DGGE and library construction methods were used to analyze the bacteria and their geobacteria, Clostridium, Bacillus and Pseudomonas in the submerged non-cultivated paddy soil. The characteristics of abundance and community structure of typical iron-reducing bacteria such as bacteria and anaerobic myxobacteria in response to flooding time and their relationship with Fe(III) reduction provide theoretical basis for further clarifying the role of microorganisms in dissimilated iron reduction and other ecological processes. The content of Fe (II) increased rapidly in the early stage (1 h-10 d) and then stabilized; the maximum reduction potential was 5.929 mg/g, the maximum reaction rate was 0.989 mg/(g.d), and the corresponding time of the maximum reaction rate (TVmax) was 2.853 D. (2) The abundance of bacteria in flooded paddy soil reached the second peak at 1 D and reached the second peak at 40 D. The process of flooding changed fine. The abundance of bacteria. The DGGE analysis based on 16S rDNA showed that the community structure of bacteria changed successively in the course of flooding: the bacteria survived by strategy r only existed in the early stage of flooding; the bacteria survived by strategy K existed in the late stage of flooding; the bacteria survived by strategy R and strategy K existed in the whole process of flooding, and the bacteria occupied by strategy K in the late stage of flooding. According to the dominance, the diversity index of dominant species increased first and then decreased in the process of submerged culture. PCA analysis classified the process of submerged water treatment into several different habitats, reflecting that the structure of bacterial community was relatively stable in the middle and later stages. Bacteroides, Proteus and Acidobacteriaceae are closely related to bacteria from paddy soils, other types of soils, activated sludge and lake sediments. (3) Abundance analysis of five typical iron-reducing bacteria showed that Bacillus was the most abundant and predominant bacteria in the whole flooding process, and Pseudomonas was abundant. At the beginning of flooding, the abundance of Clostridium and Bacillus increased rapidly and reached the maximum value in 1 day, while the abundance of Enterobacter, Pseudomonas and Anaerobic Myxobacteria was the smallest in 1 day, and then showed an upward trend, reaching the maximum at 40, 30 and 60 days respectively. (4) The community structure analysis of five typical iron-reducing bacteria showed that the community structure changed during the flooding process. Diversity analysis showed that different bacteria contributed greatly to the iron reduction process. The change of Shannon index H'was obvious, and the change of Bacillus spp. was the greatest from 1.674 h to 4.129 D. According to the PCA analysis of flooding time, five kinds of iron-reducing bacteria were divided into different habitats, and formed independent habitats in the later period of culture, which also indicated that the community in the later period of flooding was similar to that of bacteria. (5) Phylogenetic analysis based on DGGE dominant bands and clone library sequences showed that five iron-reducing bacteria were widely distributed in the soil and could be aggregated with many microorganisms with pollutant degradation and heavy metal reduction. (6) CCA analysis showed that Fe (II) concentration and pH value of paddy soil during flooding. In summary, the abundance and community structure of bacteria and their five iron-reducing bacteria responded to the flooding time respectively; iron-reducing bacteria contributed to the iron reduction process of paddy soil, and Bacillus spp. contributed the most to the iron reduction of the whole flooding process. In the late stage of flooding, the bacteria and anaerobic bacteria also made important contributions.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S154.36

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