The abundance of nirS-type denitrifiers and anammox bacteria in rhizospheres was affected by the organic acids secreted from roots of submerged macrophytes

• Published in: Chemosphere (Oxford) Vol. 240; p. 124903
• Main Authors: Yin, Xingjia, Lu, Jing, Wang, Yuchun, Liu, Guanglong, Hua, Yumei, Wan, Xiaoqiong, Zhao, Jianwei, Zhu, Duanwei
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2020
• Subjects: Anammox bacteria; Bacteria - metabolism; Biodegradation, Environmental; Denitrification - genetics; Denitrifier; Eutrophication; Hydrocharitaceae - metabolism; Lake sediments; Lakes - chemistry; Nitrogen - chemistry; Nitrogen Cycle; Organic Chemicals - metabolism; Potamogetonaceae - microbiology; Rhizosphere; Rhizosphere organic acids; Soil Microbiology; Submerged macrophytes; Denitrifier; Rhizosphere organic acids; Lake sediments; Anammox bacteria; Submerged macrophytes
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2019.124903

Excessive nitrogen has been a global concern to cause lake eutrophication. The denitrification and anammox processes are considered to be effective biological pathways for nitrogen removal. Submerged macrophytes also play a key role in the nitrogen cycle of lakes. However, the mechanism of submerged macrophytes on regulating biological nitrogen removal pathways has not been well quantified. Therefore, this study investigated the impacts of submerged macrophytes on the community structures and abundance of the nirS-type denitrifiers and anammox bacteria in the rhizospheres. The qPCR results indicated that the abundance of two bacteria in the near-rhizospheres of submerged macrophytes was significantly lower than the root compartments and non-rhizospheres, while the concentrations of organic acids in the near-rhizospheres were higher than those of the root compartments and non-rhizospheres. Redundancy analysis results illustrated that concentrations of NO3−-N, NO2−-N, citric acid and oxalic acid were the key environmental indicators which had the significant impact on the microbial community. The concentrations of citric acid and oxalic acid were negatively correlated with the nirS-type denitrifiers abundance, and the oxalic acid concentrations were negatively correlated with the anammox bacteria abundance. These results indicated that submerged macrophytes could reduce the abundance of nirS-type denitrifiers and anammox bacteria by releasing organic acids. In addition, the highest diversity of denitrifier community were found in the rhizosphere of the Hydrilla verticillata, while the highest diversity of anammox community were found in the Potamogeton maackianus rhizosphere. These results indicate that the impacts of submerged macrophytes on the biological nitrogen removal pathways were species-dependent. •Nitrogen cycle related bacteria were examined in submerged macrophyte rhizospheres.•Pseudomonas was major nirS-type denitrifiers in submerged macrophytes rhizospheres.•Jettenia, Brocadia and Kuenenia were major anammox bacteria in rhizospheres.•Lower abundance of nirS and anammox 16S rRNA genes was detected in near-rhizosphere.•Organic acid might be a key factor influencing nirS and anammox gene abundance.