Metabolism characteristics of nitrogen functional microorganisms in bioretention system under multiple dry-wet alternation

Abstract

In this study, we used metagenomic sequencing to explore the metabolism characteristics of nitrogen-cycling microorganisms in a bioretention system under multiple dry-wet alternation conditions. The results revealed that different dry-wet alternation conditions affected the composition of nitrogen-cycling microbes in bioretention soil media (BSM). In addition, the metagenomic analyses showed a higher relative abundance of key denitrifiers (Proteobacteria and Actinobacteria) under constant periods than unordered period. Furthermore, there was increased expression of nitrification functional genes and decreased expression of denitrifying functional genes during the unordered period, leading to nitrate accumulation in BSM. Under the constant dry-wet conditions, a short dry period (5 d) was shown to be beneficial to the nitrate reduction process. However, there was a risk of nitrite accumulation, which could be improved by rewetting. Moreover, our data proved that the NADH production process was inhibited in unordered period, causing nitrate accumulating. In conclusion, this study revealed that the different dry-wet alternation conditions could drive the expression of nitrogen functional genes, thus affected the biological nitrogen metabolism in bioretention systems.