Evidence for Assimilatory Nitrate Reduction as a Previously Overlooked Pathway of Reactive Nitrogen Transformation in Estuarine Suspended Particulate Matter

• DOI: 10.1021/acs.est.2c04390
• Publication Date: 2022-09-13T13:05:54Z
• Authors: Ruiwen Hu; Songfeng Liu; Weiming Huang; Qiong Nan; P. J. Strong; Muhammad Saleem; Zhengyuan Zhou; Zhiwen Luo; Fangqi Shu; Qingyun Yan; Zhili He; Cheng Wang
• Keywords: Anammox; Nitrogen Cycle

Suspended particulate matter (SPM) contributes to the loss of reactive nitrogen (Nr) in estuarine ecosystems. Although denitrification and anaerobic ammonium oxidation SPM compensate for current imbalance global (N) inputs sinks, it is largely unclear whether other pathways Nr transformation exist SPM. Here, we combined stable isotope measurements with metagenomics metatranscriptomics verify occurrence dissimilatory nitrate reduction (DNRA) Pearl River Estuary (PRE). Surprisingly, conventional functional genes DNRA (nirBD) were abundant highly expressed SPM, which was inconsistent a low potential rate. Through taxonomic comparative genomic analyses, demonstrated that nitrite reductase (NirBD) conjunction assimilatory (NasA) performed (ANR) diverse alpha- gamma-proteobacterial lineages identified as key active heterotrophic ANR bacteria. Moreover, predicted have relative higher than survey across PRE spanning 65 km. Collectively, this study characterizes previously overlooked pathway mediated by bacteria has important implications our understanding N cycling estuaries.