16S rDNA analysis of Municipal Wastewater Outflow and Environmental Water Samples in the Puget Sound

Wastewater treatment plants (WWTPs) are integral parts of the infrastructure of metropolitan areas across the world. Their role in treating both stormwater and wastewater helps minimize the impact that humans have on their surrounding environment. Wastewater treatment is an expensive endeavor that aims to balance environmental impact and cost. Current standard methods of evaluating bacterial contamination of wastewater are based on culturing samples for the number of bacterial colonies. Here, we use Oxford Nanopore sequencing as a comprehensive method for surveying the microbial composition of wastewater outflow. 16s rDNA sequencing of final effluent (FE) from the West Point Wastewater Treatment Plant in Seattle, as well as of surrounding coastal environments revealed high levels of Arcobacteraceae, a family of sewage-related bacteria, in the FE and at Discovery Park Beach. We also detected high relative levels of bacteria previously identified to be resistant to antibiotics in the FE, suggesting a need for future studies on the effects of wastewater treatment processes on bacterial viability, as well as possible links to antibiotic-resistant clinical isolates. The release of such bacteria at high levels in the Puget Sound may elevate the risk of horizontal gene transfer, potentially leading to the rise of new antibioticresistant pathogens. Routine monitoring through relatively inexpensive DNA sequencing will allow more comprehensive screening of wastewater and optimization of cost-effective treatment.