Laboratory experimental setup for structural and microbial succession studies of biofilms within simulated irrigation water distribution systems

Abstract

In the current global awareness of the water–energy–food nexus, the impact on agricultural produce of contaminants in freshwater sources has emerged as pivotal in food safety and irrigation management. Previous studies have shown that pollutants concentrate in plants following irrigation using contaminated surface freshwater. Importantly, although usually overlooked, biofilms are ubiquitous and form naturally within irrigation water distribution systems (IWDSs). Therefore, they may play a significant role in the spread of pathogenic, chemical, and environmental pollutants to irrigated agricultural produce. Our limited knowledge about IWDS biofilms and their functional attributes is largely due to the experimental challenges faced in attempting to study these biofilms in their natural environments. To address this gap, in the present study, the piping environment within an IWDS was recreated using a laboratory-based experimental system combined with a biofilm reactor. The system was designed to simulate a freshwater environment and allow the assessment of the effects of selected pollutants on engineered IWDS biofilms. To achieve this objective, the system was tested for its robustness and repeatability in terms of dynamic changes in the biofilm structure and microbial community. The biofilm structure was analyzed using state-of-the-art confocal microscopy and post-image processing and analyzed the biofilm microbial community profiles using repeated DNA extractions and next-generation sequencing. The results indicated that our laboratory-based experimental system would be well suited for use in repeatable biofilm experiments in future studies, which could focus on the effects of selected pollutants on biofilm formation in both IWDSs in particular and freshwater environments in general.