Phytoextraction is an attractive strategy for remediation of soils contaminated by heavy metal (HM), yet the effects of this practice on biochemical processes involved in soil nutrient cycling remain unknown. Here we investigated the impact of successive phytoextraction with a Cd/Zn co-hyperaccumulator Sedum alfredii (Crassulaceae) on potential nitrification rates (PNRs), abundance and composition of nitrifying communities and functional genes associated with nitrification using archaeal and bacterial 16S rRNA gene profiling and quantitative real-time PCR. The PNRs in rhizosphere were significantly (P < 0.05) lower than in the unplanted soils, and decreased markedly with planting time. The decrease of PNR was more paralleled by changes in numbers of copy and transcript of archaeal amoA gene than the bacterial counterpart. Phylogenetic analysis revealed that phytoextraction induced shifts in community structure of soil group 1.1b lineage-dominated ammonia-oxidizing archaea (AOA), Nitrosospira cluster 3-like ammonia-oxidizing bacteria (AOB) and Nitrospira-like nitrite-oxidizing bacteria (NOB). A strong positive correlation was observed between amoA gene transcript numbers and PNRs, whereas root exudates showed negative effect on PNR. This effect was further corroborated by incubation test with the concentrated root exudates of S. alfredii. Partial least squares path model demonstrated that PNR was predominantly controlled by number of AOA amoA gene transcripts which were strongly influenced by root exudation and HM level in soil. Our result reveals that successive phytoextraction of agricultural soil contaminated by HMs using S. alfredii could inhibit ammonia oxidation and thereby reduce nitrogen loss.

植物提取是修复重金属（HM）污染土壤的一种有吸引力的策略，但是这种做法对涉及土壤养分循环的生化过程的影响仍然未知。在这里，我们研究了使用古细菌和细菌16S rRNA基因谱分析和Cd / Zn超高累积量的景天草（景天科）连续植物提取对潜在硝化速率（PNRs），硝化群落的丰度和组成以及与硝化有关的功能基因的影响。定量实时PCR。根际中的PNRs显着（P <0.05）低于未种植的土壤，并且随种植时间的延长而显着下降。与细菌对应物相比，古细菌amoA基因的拷贝数和转录本数目的变化与PNR的减少更平行。进化分析表明在土壤组1.1B谱系主导氨氧化古菌（AOA）的群落结构，该植物提取诱导移Nitrosospira簇3样氨氧化细菌（AOB）和硝化螺样亚硝酸氧化细菌（NOB）。观察到amoA基因转录物数量与PNR之间有很强的正相关性，而根系分泌物对PNR则显示出负面影响。通过与浓根分泌物的温育试验进一步证实了该作用。S. alfredii。偏最小二乘路径模型表明PNR主要受AOA amoA基因转录物数量的控制，而AOA amoA基因转录物的数量受土壤根系分泌物和土壤中HM水平的强烈影响。我们的研究结果表明，使用苜蓿链球菌对被HMs污染的农业土壤进行连续的植物提取可以抑制氨氧化，从而减少氮的流失。