Sulfur-based denitrification is a promising technology in treatments of nitrate-contaminated wastewaters. However, due to weak bioavailability and electron-donating capability of elemental sulfur, its sulfur-to-nitrate ratio has long been low, limiting the support for dissimilatory nitrate reduction to ammonium (DNRA) process. Using a long-term sulfur-packed reactor, we demonstrate here for the first time that DNRA in sulfur-based system is not negligible, but rather contributes a remarkable 40.5 %–61.1 % of the total nitrate biotransformation for ammonium production. Through combination of kinetic experiments, electron flow analysis, 16S rRNA amplicon, and microbial network succession, we unveil a cryptic sulfur disproportionation (SDP) process which significantly facilitates DNRA via enhancing mass transfer and multiplying 86.7–210.9 % of bioavailable electrons. Metagenome assembly and single-copy gene phylogenetic analysis elucidate the abundant genomes, including , and , harboring complete genes for ammonification. Notably, a unique group of self-SDP-coupled DNRA microorganism was identified. This study unravels a previously concealed fate of DNRA, which highlights the tremendous potential for ammonium recovery and greenhouse gas mitigation. Discovery of a new coupling between nitrogen and sulfur cycles underscores great revision needs of sulfur-driven denitrification technology.

中文翻译：

---

被忽视的原位硫歧化促进硫基系统中异化硝酸盐还原成铵：氮回收的新见解


硫基反硝化是处理硝酸盐污染废水的一种很有前景的技术。然而，由于单质硫的生物利用度和给电子能力较弱，其硫硝比长期以来一直较低，限制了对硝酸异化还原成铵（DNRA）工艺的支持。使用长期的硫填充反应器，我们在这里首次证明硫基系统中的 DNRA 不可忽略，而是为铵生产贡献了总硝酸盐生物转化的 40.5%–61.1%。通过结合动力学实验、电子流分析、16S rRNA 扩增子和微生物网络演替，我们揭示了一种神秘的硫歧化 (SDP) 过程，该过程通过增强传质和倍增 86.7-210.9% 的生物可用电子来显着促进 DNRA。宏基因组组装和单拷贝基因系统发育分析阐明了丰富的基因组，包括 、 和 ，含有完整的氨化基因。值得注意的是，鉴定出了一组独特的自 SDP 偶联 DNRA 微生物。这项研究揭示了 DNRA 先前被掩盖的命运，凸显了铵回收和温室气体减排的巨大潜力。氮和硫循环之间新耦合的发现强调了硫驱动反硝化技术的巨大修改需求。