Antibiotic contamination amplifies the impact of foreign antibiotic-resistant bacteria on soil bacterial community.

Human activities are stimulating the presence of foreign antibiotic-resistance bacteria (ARB) in soils and antibiotic-contaminated soils are increasing continuously in the world. However, little is known about the impacts of foreign ARB on the indigenous bacterial community in antibiotic-contaminated soil. Herein, using a microcosm experiment we studied the soil bacterial community composition and function (presented with niche structure and niche breadth) in the response to a model ARB (multidrug-resistant Escherichia coli) amendment in the absence and presence of tetracycline contamination. Results demonstrated that the ARB amendment increased the diversity and niche breadth and altered the composition and niche structure of the soil bacterial community. Tetracycline contamination further enhanced these impacts probably via increasing the survival of foreign ARB in soil. Interestingly, the ARB-induced changes in the bacterial community composition and function were synchronized, which might be driven by the substantial changes in some core taxa (Proteobacteria, Bacteroidetes, Chloroflexi, and Patescibacteria). Furthermore, the impacts of the foreign ARB on soil bacterial community lasted longer than the survival of ARB in tetracycline-uncontaminated and low contaminated soils, demonstrating that the amendment of foreign ARB into soil likely challenges the stability of the soil bacterial community in a relatively long period. Overall, this study highlighted that antibiotic contamination could aggravate the impacts of the foreign ARB on soil bacterial community composition and function, resulting in the potential risks in reducing soil quality.