Diversity of anammox bacteria and abundance of functional genes for nitrogen cycling in the rhizosphere of submerged macrophytes in a freshwater lake in summer

• Published in: Journal of soils and sediments Vol. 19; no. 10; pp. 3648 - 3656
• Main Authors: Zhao, Jianwei, Xu, Yangfan, Peng, Lei, Liu, Guanglong, Wan, Xiaoqiong, Hua, Yumei, Zhu, Duanwei, Hamilton, David P.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.10.2019; Springer Nature B.V
• Subjects: Abundance; Ammonia; Ammonia monooxygenase; Ammonia-oxidizing bacteria; AmoA gene; Aquatic plants; Archaea; Bacteria; Community structure; Correlation analysis; Cycles; Dominant species; Earth and Environmental Science; Environment; Environmental Physics; Freshwater; Freshwater lakes; Freshwater plants; Gene sequencing; Genes; Inland water environment; Lake sediments; Lakes; Macrophytes; Microorganisms; NirK protein; Nitrite reductase; Nitrogen; Nitrogen cycle; Nucleotide sequence; Oxidation; PCR; Polymerase chain reaction; Redundancy; Rhizosphere; rRNA 16S; Sec 4 • Sediment-Ecology Interactions • Research Article; Sediment; Sediments; Soil Science & Conservation; Submerged plants; Substrates; Summer; Ammonia-oxidizing archaea; Rhizosphere; Denitrifying bacteria; Anammox bacteria; Submerged macrophytes; Ammonia-oxidizing bacteria
• DOI: 10.1007/s11368-019-02340-4
• ISSN: 1439-0108

Purpose Submerged plants make an important contribution to nitrogen cycling in lakes including in the rhizosphere microenvironment through microbial activities. The main objective of this study was to investigate the abundance of functional genes for nitrogen cycling and the ecological relationship between these genes in the rhizosphere sediment of a freshwater lake in summer. Materials and methods Sediment from the rhizosphere of four submerged macrophytes ( Ceratophyllum demersum , Hydrilla verticillata , Potamogeton maackianus , and Vallisneria spiralis ) was sampled in Lake Liangzi, China, in summer. The anammox bacteria community structure and abundance of five functional genes for nitrogen cycling, ammonia monooxygenase ( amoA ) of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), anammox 16S rRNA, and nitrite reductase genes ( nirK and nirS ) in the sampled sediment, were determined. Results and discussion A total of 100 anammox gene sequences were grouped into eight operational taxonomic units (OTUs) and genus Ca. Kuenenia was the dominant species in Lake Liangzi in summer. Quantitative polymerase chain reaction (qPCR) revealed that gene copies of AOA amoA (2.42 × 10 6 copies g −1 ) were more than one order of magnitude higher than those of AOB amoA (1.98 × 10 5 copies g −1 ). The nirS gene (4.13 × 10 8 copies g −1 ) was more abundant than the nirK gene (7.28 × 10 7 copies g −1 ). There was no significant difference in the abundance of the AOB amoA gene among the rhizosphere of the four macrophytes. Redundancy analysis (RDA) showed a positive correlation between the abundance of the anammox 16S rRNA gene, AOA amoA and AOB amoA , which suggested two of these microbes may have provided a substrate for anammox bacteria in summer. Conclusions The diversity of anammox in the rhizosphere of submerged macrophytes of the freshwater lake in summer was very low, but the plant species could affect the abundance of most nitrogen circulating bacteria, especially for anammox bacteria. Anammox 16S rRNA gene was positively correlated with four other functional genes, indicating that all four genes had significant effects on anammox bacteria.