16S rRNA based profiling of extracellular DNA from wastewaters. exDNA-WWTPs

Wastewater treatment plants have been reported as major anthropogenic reservoirs for the spread of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) into the environment (esp. aquatic), worldwide. While most studies mainly focus on the intracellular DNA (iDNA), extracellular DNA (exDNA) accounting for a significant proportion of the total DNA in wastewater, was usually neglected. According to a One Health approach, this study focusses on wastewaters of municipal, clinical and livestock origins (n=45) that undergo different treatment processes (i.e., conventional activated sludge, ultrafiltration, and ozonation). Water samples were analysed for 12 target ARGs as indicators of the different compartments associated with iDNA and exDNA by qPCR. Taxonomic profiling of exDNA-fractions was conducted by sequencing the V3–V4 hypervariable regions of 16S rRNA gene.