Jones Zackary L, Jasper Justin T, Sedlak David L, Sharp Jonathan O
ReNUWIt Engineering Research Center‡.
Department of Civil and Environmental Engineering, Colorado School of Mines Golden, Colorado, USA.
Appl Environ Microbiol. 2017 Jul 17;83(15). doi: 10.1128/AEM.00782-17. Print 2017 Aug 1.
Open-water unit process wetlands host a benthic diatomaceous and bacterial assemblage capable of nitrate removal from treated municipal wastewater with unexpected contributions from anammox processes. In exploring mechanistic drivers of anammox, 16S rRNA gene sequencing profiles of the biomat revealed significant microbial community shifts along the flow path and with depth. Notably, there was an increasing abundance of sulfate reducers ( and other ) and anammox microorganisms () with depth. Pore water profiles demonstrated that nitrate and sulfate concentrations exhibited a commensurate decrease with biomat depth accompanied by the accumulation of ammonium. Quantitative PCR targeting the anammox hydrazine synthase gene, , revealed a 3-fold increase in abundance with biomat depth as well as a 2-fold increase in the sulfate reductase gene, These microbial and geochemical trends were most pronounced in proximity to the influent region of the wetland where the biomat was thickest and influent nitrate concentrations were highest. While direct genetic queries for dissimilatory nitrate reduction to ammonium (DNRA) microorganisms proved unsuccessful, an increasing depth-dependent dominance of and diatoms that have previously been functionally linked to DNRA was observed. To further explore this potential, a series of microcosms containing field-derived biomat material confirmed the ability of the community to produce sulfide and reduce nitrate; however, significant ammonium production was observed only in the presence of hydrogen sulfide. Collectively, these results suggest that biogenic sulfide induces DNRA, which in turn can explain the requisite coproduction of ammonium and nitrite from nitrified effluent necessary to sustain the anammox community. This study aims to increase understanding of why and how anammox is occurring in an engineered wetland with limited exogenous contributions of ammonium and nitrite. In doing so, the study has implications for how geochemical parameters could potentially be leveraged to impact nutrient cycling and attenuation during the operation of treatment wetlands. The work also contributes to ongoing discussions about biogeochemical signatures surrounding anammox processes and enhances our understanding of the contributions of anammox processes in freshwater environments.
开放水域单元工艺湿地拥有一个底栖硅藻和细菌群落，能够从经处理的城市污水中去除硝酸盐，其中厌氧氨氧化过程做出了意想不到的贡献。在探索厌氧氨氧化的机制驱动因素时，生物膜的16S rRNA基因测序图谱显示，微生物群落沿水流路径和深度发生了显著变化。值得注意的是，随着深度增加，硫酸盐还原菌（以及其他菌）和厌氧氨氧化微生物的丰度不断增加。孔隙水剖面表明，硝酸盐和硫酸盐浓度随生物膜深度呈相应下降，同时伴有铵的积累。针对厌氧氨氧化肼合酶基因的定量PCR显示，其丰度随生物膜深度增加了3倍，硫酸盐还原酶基因也增加了2倍。这些微生物和地球化学趋势在湿地进水区域附近最为明显，那里的生物膜最厚，进水硝酸盐浓度最高。虽然对异化硝酸盐还原为铵（DNRA）微生物的直接基因查询未成功，但观察到与DNRA功能相关的和硅藻在深度依赖性上的优势不断增加。为了进一步探索这种可能性，一系列含有现场采集生物膜材料的微观世界证实了该群落产生硫化物和还原硝酸盐的能力；然而，只有在存在硫化氢的情况下才观察到大量铵的产生。总体而言，这些结果表明生物源硫化物诱导了DNRA，这反过来可以解释为维持厌氧氨氧化群落，硝化废水必需共同产生铵和亚硝酸盐。本研究旨在加深对在铵和亚硝酸盐外源贡献有限的工程湿地中厌氧氨氧化为何以及如何发生的理解。通过这样做，该研究对如何利用地球化学参数来影响处理湿地运行期间的养分循环和衰减具有启示意义。这项工作也有助于正在进行的关于厌氧氨氧化过程周围生物地球化学特征的讨论，并增进我们对厌氧氨氧化过程在淡水环境中贡献的理解。
