Fe (Ⅱ)对反硝化过程及其功能微生物群落的影响

以华南稻田土壤为研究对象，通过室内模拟控制实验，研究了Fe （Ⅱ）对厌氧稻田土壤中反硝化过程及其功能微生物群落结构组成与相对丰度的影响.结果表明，加入Fe （Ⅱ）减缓了土壤中NO₃^-的还原，但促进了NO₂^-的还原和N₂O的生成；同时Fe （Ⅱ）只在Soil+Fe （Ⅱ）+NO₃^-处理中发生氧化.通过定量PCR结果发现，Fe （Ⅱ）的加入提高了亚硝酸盐还原基因nirS和N₂O还原基因nosZ的拷贝数；但降低了细胞膜硝酸盐还原基因narG的拷贝数.通过高通量和克隆文库分析发现，Fe （Ⅱ）的加入主要对napA-周质硝酸盐还原微生物群落结构有明显影响，Soil+NO₃^-处理中优势菌是Dechloromonas，而Soil+Fe （Ⅱ）+NO₃^-处理中为Azonexus、Dechloromonas和Azospira.Fe （Ⅱ）对厌氧稻田中的反硝化过程及其功能微生物群落具有显著影响，这对了解华南红壤地区稻田体系中的氮元素循环与铁元素转化的关系具有重要意义.

Effect of Fe(Ⅱ) on denitrification and associated functional microbial communities

Paddy soil was collected from Southern China and used as an inoculum in an anoxic experiment to investigate the effect of Fe(Ⅱ) oxidation on denitrification and associated microbial communities. The results showed that the presence of Fe(Ⅱ) slowed down the NO₃^- reduction, but facilitated the NO₂^- reduction and N₂O formation; meanwhile Fe(Ⅱ) oxidation was observed only in the Soil+Fe(Ⅱ)+NO₃^- treatment. The real-time quantitative PCR analysis demonstrated that the presence of Fe(Ⅱ) increased the copy numbers of nitrite reduction gene (nirS) and nitrous oxide (N₂O) reduction gene (nosZ), but inhibited the activity of membrane nitrate reduction gene (narG). The results of high-throughput sequencing and clone library exhibited that the presence of Fe(Ⅱ) significantly influences the microbial communities affiliated with periplasmic nitrate reduction gene (napA). The most abundant napA-based nitrate reducer was Dechloromonas in the Soil+NO₃^- treatment, while those were Azonexus, Dechloromonas and Azospira in the Soil+Fe(Ⅱ)+NO₃^- treatment. In summary, Fe(Ⅱ) significantly influences the denitrification process and the associated microbial communities in anoxic paddy soil. This can provide better understanding of the relationship between the nitrogen cycling and the iron transformation in the red paddy soil from South China.