Temperature effects on invadibility of river microbial communities through wastewater bacteria

We here determined if climate change does affect AMR in river microbial communities by investigating temperature effects on both, the intrinsic river biofilm resistome as well as the outcome of invasion events of ARB and ARG from wastewater into these biofilms. To achieve this, river biofilms were grown on glass slides which were immersed into a pristine sub-tributary of river Elbe in Germany for one month. The biofilms were then transferred to artificial laboratory recirculation river water flume systems. These flume systems were kept at three different temperatures of 20C, 25C and 30C. Biofilms were allowed to acclimatize for one week at the respective temperature. Thereafter, biofilms were exposed to a single pulse of wastewater for 2 weeks. Throughout the experiment biofilms were destructively sampled and the biofilm resistome was characterized using high throughput qPCR, while the biofilm microbial community composition was analyzed using 16S rRNA gene-based amplicon sequencing. This allowed determining the time-resolved invasion dynamics of wastewater-born ARB and ARGs into the river biofilms as a function of temperature. In addition, control group flumes without wastewater addition were run to determine the effect of increasing temperatures on microbiome and resistome composition.