Effects of enrofloxacin on soil nitrification and denitrification: A microbiological study

Extensive use of enrofloxacin (ENR) leads to its widespread presence in soil, which seriously threatens the soil ecological environment and biogeochemical cycles. Thus, it is very important to comprehend the fate of ENR and its effect on nitrogen cycling in farmland soil. In this investigation, quantitative real-time PCR and 16 S rRNA genes amplicon sequencing were used to analyze the microbiological mechanism of the effects of ENR on the soil nitrification and denitrification processes of farmland. The results showed that the addition of ENR suppressed the ammoniation process, leading to a decline in NH4+-N content. Additionally, ENR led to a decrease in the soil nitrification potential by decreasing the relative abundance of Nitrosomonas and Nitrosospira. However, ENR inhibited the relative abundance of narG, as well as the activity of nitrate reductase, which led to the accumulation of NO3--N. Furthermore, ENR increased the possibility of nitrous oxide emissions by increasing the relative abundances of Flavobacterium, Bacillus and Aeromonas, as well as those of nirS and nosZ. This study provided data to support for the ecological impact and risk assessment of ENR on nitrogen cycling in farmland soil.