Effect of feeding conditions on the degradation of tetracycline in sewage sludge by earthworm

•This work set two ways of swallowing: sequential swallowing and repeated swallowing.•The digestion of earthworms enhanced the degradation rate of TC in municipal sludge.•The bacterial community in earthworm intestine changed under different feeding ways. In this study, the changes in the enzymatic activity and bacterial communities inhabiting the earthworm gut were investigated to determine the correlation between feeding conditions and tetracycline (TC) degradation. Two TC concentrations (high and low) were fed to earthworms using either the sequential swallowing or repeated swallowing technique. The repeated swallowing feeding technique was found to have a better effect on the degradation rate of TC. The peroxidase and catalase activities in earthworms fed using the sequential swallowing technique were higher than those in earthworms fed using the repeated swallowing technique. When the sequential swallowing technique was used, the TC degradation rate was found to be negatively correlated with the abundance of Clostridium, Hyphomicrobium, and Streptomyces, whereas when the repeated swallowing technique was used for feeding the earthworms, the TC degradation rate was positively correlated with the abundance of 18 bacterial species, including Clostridium, Hyphomicrobium, and Fodinicola.