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

Abstract

The abundance of nirS-type denitrifiers and anammox bacteria in rhizospheres were affected by the organic acids secreted from roots of submerged macrophytes Abstract：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 were 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.The RDA 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.

A review on nirS-type and nirK-type denitrifiers via a scientometric approach coupled with case studies

“…It was more likely that organic acids promoted the rapid growth of other heterotrophic bacteria, and nirS -type denitrifiers were in a weak position competing for carbon substrates. 69…”

Higher Food Yields and Lower Greenhouse Gas Emissions from Aquaculture Ponds with High-Stalk Rice Planted

“…The reduction of nir S primarily presented in the flooding stages (SI and SII) (Figure ). The denitrification process was sensitive to the availability of O 2 and substrate N in the flooded anaerobic sediment. , Planting high-stalk rice increased the O 2 supply and decreased the content of NO 3 – in the sediment (Figures and ), thus may inhibit the denitrification and decrease the abundance of nir S. In addition, the abundance of nir S negatively correlated with the contents of organic acids in the anaerobic soils . Rice roots can secrete the organic acids in the rhizospheric soil, thus may inhibit the growth of nir S-type denitrifiers.…”

“…In addition, the abundance of nirS negatively correlated with the contents of organic acids in the anaerobic soils. 43 Rice roots can secrete the organic acids in the rhizospheric soil, 44 thus may inhibit the growth of nirS-type denitrifiers.…”

Effect of Aquatic Vegetation Restoration after Removal of Culture Purse Seine on Phytoplankton Community Structure in Caizi Lakes

“…The rhizosphere of the aquatic vegetation secretes organic substances. This can affect denitrifying bacteria and ammonifying bacteria in sediments and promote the nitrogen cycle [34], all of which may have contributed to the significantly lower TN concentration in Lake Baitu than in Lake Caizi and Lake Xizi in summer. To sum up, the improvement of water quality in the Caizi Lakes was closely related to the restoration of the aquatic vegetation.…”