Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen 361102, China.
Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen 361102, China; State Key Laboratory of Marine Environmental Sciences, Xiamen University, Xiamen 361102, China.
Sci Total Environ. 2021 Jun 15;773:145632. doi: 10.1016/j.scitotenv.2021.145632. Epub 2021 Feb 5.
Mangrove ecosystems are natural nitrogen removal systems that are primarily mediated by nitrogen cycle microorganisms, but their relative contributions to nitrogen transformation and removal in mangrove sediments under anthropogenic nitrogen input needs further resolution and characterization. Here, we investigated the responses and the relative contributions of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), anaerobic ammonium oxidizing (anammox) bacteria and denitrifying bacteria after spiking urea into mangrove sediments incubated in a laboratory microcosm experiment for four weeks. During incubation, the diversity, abundances and transcription levels of the hzo genes for anammox bacteria, amoA genes for AOA and AOB, and nirS genes for denitrifying bacteria were monitored using targeted gene clone library analyses and quantitative PCR assays at the DNA and RNA levels. The results showed that mangrove sediments harbour habitat-specific anammox bacteria which related to Candidatus Scalindua and Candidatus Kuenenia clades. Mangrove specific AOA related to deep branched clades within Candidatus Nitrososphaera and Candidatus Nitrosotalea, and AOB related to Nitrosomonas and Nitrosospira were also detected in the collected sediment samples. Growth and activity of AOA were detected at all levels of amendment of nitrogen input, whereas AOB growth was detectable only at the high-level nitrogen input (1.5 mg urea per gram of dry sediment) with no amoA transcripts and lower abundance than AOA. The abundance and transcription levels of the nirS gene were higher (~1000 times) than those of the hzo gene in all groups. Pearson correlation analysis demonstrated that the abundance of both AOA and AOB amoA genes had a significant positive correlation with the nirS gene (p < 0.01). These results indicated that nitrification (primarily mediated by the AOA)-denitrification process played the most important role in nitrogen removal from the amendment of nitrogen short-term input in the mangrove sediments.
红树林生态系统是天然的氮去除系统，主要由氮循环微生物介导，但它们在人为氮输入下对红树林沉积物中氮转化和去除的相对贡献仍需进一步阐明和表征。在这里，我们研究了在实验室微宇宙实验中，向红树林沉积物中添加尿素后，氨氧化古菌（AOA）、氨氧化细菌（AOB）、厌氧氨氧化（anammox）细菌和反硝化细菌的响应及其相对贡献。在培养过程中，通过靶向基因克隆文库分析和 DNA 和 RNA 水平的定量 PCR 检测，监测了 anammox 细菌的 hzo 基因、AOA 和 AOB 的 amoA 基因以及反硝化细菌的 nirS 基因的多样性、丰度和转录水平。结果表明，红树林沉积物中含有与 Candidatus Scalindua 和 Candidatus Kuenenia 丛相关的特有 anammox 细菌。从采集的沉积物样本中还检测到与 Candidatus Nitrososphaera 和 Candidatus Nitrosotalea 内深分支丛相关的特有 AOA，以及与 Nitrosomonas 和 Nitrosospira 相关的 AOB。在所有氮输入水平的添加中都检测到 AOA 的生长和活性，而 AOB 的生长仅在高氮输入水平（1.5 mg 尿素/克干沉积物）下可检测到，其 amoA 转录物和丰度均低于 AOA。nirS 基因的丰度和转录水平均高于所有组中的 hzo 基因（高出约 1000 倍）。Pearson 相关性分析表明，AOA 和 AOB amoA 基因的丰度与 nirS 基因呈显著正相关（p<0.01）。这些结果表明，硝化（主要由 AOA 介导）-反硝化过程在红树林沉积物中对短期氮输入添加的氮去除中起着最重要的作用。
