Nitrite- and N2O-reducing bacteria respond differently to ecological factors in saline lakes
Xiaoxi Sun, Jian Yang, Hongchen Jiang, Beichen Wang, Haiyi Xiao, Zhanling Xie, Jinbin Han, Xi‐Ying Zhang, Jianxin Xu, Dafei Gong, Xuexia Zhang, Yaoyao Wang
Abstract
The distribution of nitrite- and N2O-reducing bacteria is key to potential N2O emission from lakes. However, such information in highland saline lakes remains unknown. Here, we investigated the abundance and community composition of nitrite- and N2O-reducing bacteria in the sediments of six saline lakes on the Qing-Tibetan Plateau. The studied lakes covered a wide range of salinity (1.0-340.0 g/L). Results showed that in the studied saline lake sediments, nitrite-reducing bacteria were significantly more abundant than N2O-reducing bacteria, and their abundances ranged 7.14 × 103-8.26 × 108 and 1.18 × 106-6.51 × 107 copies per gram sediment (dry weight), respectively. Nitrite-reducing bacteria were mainly affiliated with α-, β- and γ-Proteobacteria, with β- and α-Proteobacteria being dominant in low- and high-salinity lakes, respectively; N2O-reducing bacterial communities mainly consisted of Proteobacteria (α-, β-, γ- and δ-subgroups), Bacteroidetes, Verrucomicrobia, Actinobacteria, Chloroflexi, Gemmatimonadetes and Balneolaeota, with Proteobacteria and Bacteroidetes/Verrucomicrobia dominating in low- and high-salinity lakes, respectively. The nitrite- and N2O-reducing bacterial communities showed distinct responses to ecological factors, and they were mainly regulated by mineralogical and physicochemical factors, respectively. In response to salinity change, the community composition of nitrite-reducing bacteria was more stable than that of N2O-reducing bacteria. These findings suggest that nitrite- and N2O-reducing bacteria may prefer niches with different salinity.