Distinct response of nitrogen metabolism to exogenous cadmium (Cd) in river sediments with and without Cd contamination history

Aomei Guan; Qiang Peng; Weihang Zhang; Weixiao Qi; Chengzhi Hu; Jiuhui Qu

doi:10.1016/j.watres.2025.123104

Distinct response of nitrogen metabolism to exogenous cadmium (Cd) in river sediments with and without Cd contamination history

Water Res. 2025 Jan 6:274:123104. doi: 10.1016/j.watres.2025.123104. Online ahead of print.

Authors

Aomei Guan¹, Qiang Peng², Weihang Zhang³, Weixiao Qi⁴, Chengzhi Hu², Jiuhui Qu³

Affiliations

¹ Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; China Academy of Urban Planning & Design, Beijing 100044, China.
² Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
³ Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
⁴ Center for Water and Ecology, State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China. Electronic address: [email protected].

PMID: 39793158
DOI: 10.1016/j.watres.2025.123104

Abstract

The role of metal resistance on nitrogen metabolism function and community resilience against Cd is important for elucidating the evolutionary dynamics of key ecological functions in river ecosystems. In this study, the response of nitrogen transforming function to Cd exposure in river sediments from the Yangtze River Basin with varying levels of heavy metal contamination history (Cd-contaminated and Cd-free sediments) was compared to understand how Cd influenced nitrogen metabolism under varying metal resistance conditions. The results showed that chronic and persistent Cd pollution of sediments caused an elevation of transport efflux metal resistance genes (MRGs) and a reduction in the uptake MRGs, leading to a stronger tolerance to Cd for Cd-contaminated sediment than Cd-free ones. Specifically, denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA) respectively responded to Cd through different mechanisms. Exogenous Cd (5-100 mg kg^-1) influenced denitrification rates (-70 %-100 % deviation to control group) by regulating key genera (Thiobacillus, Magnetospirillum, Sideroxydans etc.) and gene clusters for denitrification. Both adaptive nature of anammox bacteria and co-regulation of key genera (Candidatus_Scalindua, Candidatus_Jettenia, Planctomyces etc.) and gene hzsA were drivers of differential responses in sediments from various contamination history. Environmental factors rather than contamination history, key genera or genes were probably critical ones determining Cd-resistance in DNRA, being more tolerant to Cd in sediments with higher TOC and NH₄⁺. Stimulation of N₂O reduction process (genera Gemmatimonas and Gemmatirosa and genes nosZ) in Cd-contaminated sediments by exogenous Cd lowered N₂O emission risk, whereas the reverse was true for Cd-free sediments. These results enrich our understanding about the linkages among MRGs and nitrogen reduction functions in river.

Keywords: Anammox; Cadmium; Denitrification; Functional genes; Metal resistance genes; Microbial community.