Fates of Bacterial/Archaeal Communities and Antibiotic Resistance Genes Under Azithromycin and Copper Combined Pollution: The Gradient Increasing and Decreasing Exposure Modes

Abstract

Bacterial and archaeal dissimilarity and the responses of antibiotic resistance genes (ARGs) to azithromycin (AZM) and copper combined pollution in activated sludge system under gradient increasing (from 0.5 to 10 mg/L) and decreasing exposure (from 10 to 0.5 mg/L) modes were investigated. Nitrification was inhibited more obviously under gradient increasing exposure mode. Responses of bacterial diversity and structure to combined pollutions were more obvious, while archaeal structure was susceptible to both exposure modes. The dominant bacterial and archaeal compositions (Hyphomicrobium, Euryarchaeota, etc.) were affected by two exposure modes, except rare archaea. There were more positive correlations between bacteria and archaea, and Nitrospira was keystone genus. Ammonia-oxidizing archaea (Nitrososphaera_viennensis) and complete ammonia oxidizers (Nitrospira_sp_ENR4) were enriched under gradient increasing and decreasing exposure modes, respectively. 50 ARG subtypes were detected and specific ARG subtypes proliferated in two exposure modes, respectively, and bacteria and archaea were the common hosts for 24 of them.

Keywords: Combined pollution, Gradient increasing and decreasing exposure modes, Bacterial and archaea communities, Antibiotic resistance genes, Potential hosts