Molecular analysis of microbial nitrogen transformation and removal potential in the plant rhizosphere of artificial tidal wetlands across salinity gradients

Manping Zhang; Yuanyuan Peng; Pan Yan; Jung-Chen Huang; Shengbing He; Shanshan Sun; Xiaohui Bai; Yun Tian

doi:10.1016/j.envres.2022.114235

Molecular analysis of microbial nitrogen transformation and removal potential in the plant rhizosphere of artificial tidal wetlands across salinity gradients

Environ Res. 2022 Dec;215(Pt 1):114235. doi: 10.1016/j.envres.2022.114235. Epub 2022 Aug 30.

Authors

Manping Zhang¹, Yuanyuan Peng², Pan Yan², Jung-Chen Huang³, Shengbing He⁴, Shanshan Sun⁵, Xiaohui Bai⁶, Yun Tian⁷

Affiliations

¹ School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China; School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
² School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China.
³ Department of Environmental Engineering, National Cheng Kung University, Tainan City 701, Taiwan.
⁴ School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China. Electronic address: heshengbing@sjtu.edu.cn.
⁵ School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China. Electronic address: sunss2017@sjtu.edu.cn.
⁶ School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
⁷ Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen 361102, PR China.

PMID: 36055394
DOI: 10.1016/j.envres.2022.114235

Abstract

This study explored the microbial nitrogen transformation and removal potential in the plant rhizosphere of seven artificial tidal wetlands under different salinity gradients (0-30‰). Molecular biological and stable isotopic analyses revealed the existence of simultaneous anammox (anaerobic ammonium oxidation), nitrification, DNRA (dissimilatory nitrate reduction to ammonium) and denitrification processes, contributing to nitrogen loss in rhizosphere soil. The microbial abundances were 2.87 × 10³-9.12 × 10⁸ (nitrogen functional genes) and 1.24 × 10⁸-8.43 × 10⁹ copies/g (16S rRNA gene), and the relative abundances of dissimilatory nitrate reduction and nitrification genera ranged from 6.75% to 24.41% and from 0.77% to 1.81%, respectively. The bacterial 16S rRNA high-throughput sequencing indicated that Bacillus, Zobellella and Paracoccus had obvious effects on nitrogen removal by heterotrophic nitrifying/aerobic denitrifying process (HN-AD), and autotrophic nitrification (Nitrosomonas, Nitrospira and Nitrospina), conventional denitrification (Bradyrhizobium, Burkholderia and Flavobacterium), anammox (Candidatus Brocadia and Candidatus Scalindua) and DNRA (Clostridium, Desulfovibrio and Photobacterium) organisms co-existed with HN-AD bacteria. The potential activities of DNRA, nitrification, anammox and denitrification were 1.23-9.23, 400.03-755.91, 3.12-35.24 and 30.51-300.04 nmolN₂·g^-1·d^-1, respectively. The denitrification process contributed to 73.59-88.65% of NO_x^- reduction, compared to 0.71-13.20% and 8.20-15.42% via DNRA and anammox, as 83.83-90.74% of N₂ production was conducted by denitrification, with the rest through anammox. Meanwhile, the nitrification pathway accounted for 95.28-99.23% of NH₄⁺ oxidation, with the rest completed by anammox bacteria. Collectively, these findings improved our understanding on global nitrogen cycles, and provided a new idea for the removal of contaminants in saline water treatment.

Keywords: Anammox and DNRA; Conventional nitrification and denitrification; Heterotrophic nitrifying/aerobic denitrifying bacteria; Rhizosphere soil; Salinity gradients; Tidal flow constructed wetlands.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Ammonium Compounds*
Bacteria / genetics
Bacteria / metabolism
Denitrification
Nitrates / analysis
Nitrogen* / analysis
Oxidation-Reduction
RNA, Ribosomal, 16S
Rhizosphere
Salinity
Soil
Wetlands

Substances

Ammonium Compounds
Nitrates
RNA, Ribosomal, 16S
Soil
Nitrogen