Wastewater effluents influence the microbiome and the resistome of the receiving water

Wastewater treatment plants (WWTPs) are a hotspot for the selection of Antibiotic Resistance Genes (ARGs), and for their spread into the environment. The fate of the ARGs released into open waters (lakes, rivers, and oceans) through WWTP outflows and the response of the resident microbial communities is of primary importance in assessing the cycle of a resistance, and thus the potential transmission to human pathogens. Treated WWTP effluents include peculiar bacterial communities (105-106 cells ml-1), with different vitality and ARGs load. What is the fate of ARGs released through WWTP effluents into open waters? How does this point source pollution impact on the natural environment?Is there a risk of permanent contamination, and if yes, does dilution of the effluent and ecology of the receiving water body matter? Once in the receiving water body, bacteria and ARGs from the WWTP effluent are exposed to a number of ecological interactions with the new environment and its microbial community. The fate of the introduced bacteria is thus regulated by ecology: Spatial (in lakes or seas with constant water mass) and temporal (in rivers, with variable water flow) dilution matters.