Exposure to environmental stressors decreases the resilience of river microbial communities towards invasion by foreign resistant bacteria

The release of wastewater treatment plant effluents into rivers exposes the river microbiome to a high load of antibiotic resistant bacteria (ARB) along with complex mixtures of abiotic pollutants acting as stressors. To understand the proliferation of antimicrobial resistance (AMR) it is crucial to determine the factors that govern invasion of ARB into the river microbiome. Consequently, we here aim at elucidating how the resilience of the resident microbial communities against invasion by foreign ARB is affected by co-released stressors. To achieve this, we grew natural microbial biofilms on glass slides in rivers for one month. The biofilms were then transferred to laboratory, recirculating flume systems and exposed to a single pulse of a model resistant invader bacterium (E. coli) either in presence or absence of stress induced by Cu2+. The invasion dynamics of E. coli into the biofilms were then monitored for 14 days. Despite an initially successful introduction of E. coli into the biofilms, independent of the imposed stress, over time the invader perished in absence of stress. However, under stress the invading strain successfully established and proliferated in the biofilms. Noteworthy, the increased establishment success of the invader coincided with a loss in microbial community diversity under stress conditions, likely due to additional niche space becoming available for the invader. In conclusion, we demonstrate that the intrinsic resilience of the river microbiome towards invasion by ARB is strongly linked with maintaining diversity and that co-exposure to stressors that disrupt community diversity and structure increases long-term invasion success.Link to OA paper: https://www.biorxiv.org/content/10.1101/2022.11.19.517188v1