Nitrogen (N) and carbon (C) biogeochemical processes, such as denitrification and organic matter decomposition, are vital for regulating ecological functions. The continuous and increasing introduction of antibiotics into the environment has led to antibiotics residues in waters, soils and sediments, which may pose adverse effects on biogeochemical processes and microbial communities. Therefore, how antibiotic residues affect N and C cycling processes and associated microbial communities has been of a great concern. 

Supervised by Prof. LIU Wenzhi and YANG Yuyi from Wuhan Botanical Garden, HE Gang and JIANG Xiaoliang conducted 44-day incubation experiments to examine the effect of tetracycline on nitrification, denitrification, and carbon dioxide (CO₂) and methane (CH₄) emissions in sediments with and without biochar addition. 

No significant difference was observed in N and C cycling rates in the sediments throughout the incubation period among the control and tetracycline alone treatments. However, the tetracycline + biochar treatment significantly enhanced the potential denitrification rate and increased the emission of CO₂ and CH₄ in sediments. Regarding to microbial communities, tetracycline alone treatment greatly reduced N- and C-cycling genes abundance in short term, but increased relative abundance of several resistance genes.  

The study reveals that non-therapeutic concentrations of tetracycline do not reduce sediment N and C cycling rates, but decrease microbial abundance in short term, and increase the risk of antibiotic resistance genes dissemination in the environment in long term. 

This study was financially supported by the National Natural Science Foundation of China, the Youth Innovation Promotion Association of the Chinese Academy of Sciences and Natural Science Foundation of Hubei Province.  

The results have been published in Chemosphere entitled “Effects of tetracycline on nitrogen and carbon cycling rates and microbial abundance in sediments with and without biochar amendment”. 

Effects of tetracycline on nitrification (PNR), denitrification (PDR), and CO₂ and CH₄ emissions with and without biochar addition (Image by WBG)