稻田硝酸盐异化还原成铵细菌群落结构的垂向分布特性

硝酸盐异化还原成铵（Dissimilatory nitrate reduction to ammonium，DNRA）过程，可将土壤中的NO₃^-/NO₂^-还原成NH₄⁺-N以被作物吸收利用，有助于土壤中氮素的保存.选择位于广东韶关市和吉林安图县的两块稻田为研究对象，通过分子生物学方法和高通量测序技术，深入探究了两种稻田土壤（0~1 m）中DNRA细菌丰度和群落结构的垂向分布特性.结果显示：两种稻田土壤中DNRA细菌更多的存在于表层土壤（0~20 cm）中，丰度最低值均出现在深层土壤（90~100 cm）中，且表层样品群落结构的多样性大于深层样品；两个稻田样品间的群落结构体现出明显的空间异质性，安图稻田样品DNRA细菌的丰度和群落结构多样性均大于韶关稻田样品；其中，相对丰度较高的Anaeromyxobacter（28.67%）、Caldimicrobium（19.49%）、Nitrospira（10.90%）和Chthoniobacter（9.15%）是两个稻田中DNRA细菌群落组成中的关键菌属.相关性分析表明，总硫（TS）、有机质（TOM）、含水率（MC）、碳氮比（C/N）与DNRA细菌丰度之间均有显著正相关性（p<0.01，n=20），偏碱性、有机质丰富、氮源缺乏、碳源丰富且C/N较高的环境及适宜的含水率是稻田垂向生态系统中DNRA细菌适宜的生存环境.

Vertical distribution of community composition of dissimilatory nitrate reduction to ammonium bacteria in paddy soils

Dissimilatory nitrate reduction to ammonium (DNRA) reduces NO₃^-/NO₂^- to NH₄⁺-N for crop uptake and utilization, which contributes to the preservation of nitrogen in the soil. In this study, two paddy fields in Shaoguan City of Guangdong Province and Antu County of Jilin Province were selected as the research objects. The molecular biology methods and high-throughput sequencing techniques were used to explore the vertical distribution of DNRA bacterial abundance and community structure in two paddy soils (0~1 m). The results show that more DNRA bacteria existed in surface soil (0~20 cm) and the lowest abundances were found in deep soil (90~100 cm), the diversity of community structure in surface soil samples was greater than that in deep soil samples. The microbial community structure between the two paddy field samples show obvious spatial heterogeneity. The abundance and diversity of DNRA bacteria in Antu paddy soil samples were higher than those in Shaoguan paddy soil; Anaeromyxobacter (28.67%), Caldimicrobium (19.49%), Nitrospira (10.90%) and Chehoniobacter (9.15%) with relatively high abundance were the key bacterial genera in DNRA bacterial community composition in the two paddy fields. The correlation analysis results show that there are significant positive correlations between TS (Total sulfur), TOM (Total organic matter), MC (Moisture content), C/N and bacterial abundance of DNRA (p<0.01, n=20). In summary, the alkaline environment, rich organic matter, lack of nitrogen, rich carbon and high C/N ratio, and suitable water content are the suitable living environment for DNRA bacteria in vertical ecosystem of paddy field.