Antibiotic resistance gene abundance and bacterial community structure in soils altered by Ammonium and Nitrate Concentrations

Antibiotic resistance genes (ARGs) in soils pose a risk to ecological and human health, and are considered emerging pollutants. Application of nitrogen fertilizer affects the soil bacterial community structure and could be a trigger for the development of ARGs. This study explored the effects of two forms of nitrogen (NH4+-N and NO3−-N) on the abundance of six ARGs (blaTEM-1, cmlA, str, sul1, tetO, and tnpA-4) and bacterial community structure in soils using quantitative polymerase chain reaction and high-throughput sequencing. Our results show that the addition of 100–200 mg kg−1 NH4+-N or NO3−-N increased the relative abundance of ARGs but decreased 16S rRNA gene abundance. Nitrogen addition at a rate of 100 mg kg−1 NH4+-N significantly reduced the abundance and diversity of the bacterial community, and the community structure differed in soil receiving NH4+-N and NO3−-N treatments. Pearson correlation and redundancy analysis supported a correlation between the soil bacterial community and ARGs with the addition of NH4+-N or NO3−-N. The increase in ARGs abundance with inorganic N may be ascribed to the changes in host bacterial communities. These findings suggest that NH4+-N and NO3-N application may trigger the development of ARGs in soil bacterial communities, and could be another risk factor in addition to the well-known effects of antibiotic exposure from animal manure on ARGs abundance in soil. We recommend that future work on this topic be attentive to experimental designs that include appropriate controls and references to improve understanding of the ARGs profiles in the soil bacterial communities.