Pharmaceutical-contaminated water irrigation impacts the human pathobiome of soil and alters aphid-endosymbiont dynamics

The use of reclaimed water for agricultural irrigation presents a sustainable strategy to address water scarcity, yet it may introduce residual pharmaceuticals that persist despite treatment. This study investigates the ecological impacts of irrigation with pharmaceutical-contaminated water on plants, soil microbial communities, aphid life history traits, and aphid-associated bacterial symbionts within the Cucurbita pepo - Aphis gossypii model system. Plants were irrigated with water spiked with some of the most common antibiotics found in wastewater, including clarithromycin, trimethoprim, clindamycin, sulfamethoxazole, azithromycin, and ofloxacin, as well as the pharmaceuticals venlafaxine and metoprolol. While overall soil microbial diversity remained unchanged, potentially pathogenic bacteria, such as Afipia, Methylobacterium, Paracoccus, and Saccharopolyspora, exhibited increased abundance, raising concerns about potential human health risks. However, no significant changes were detected in class 1 integron (a proxy of antibiotic resistance) abundance, suggesting that the concentrations used in this study did not exert sufficient selective pressure. Plant traits, aphid survival and fecundity were unaffected by chemical exposure, yet a reduction in endosymbiont abundance was observed, indicating potential long-term ecological consequences for aphid populations. These findings highlight the need for further research on the long-term effects of pharmaceutical contamination in agroecosystems, particularly regarding its implications for biodiversity, soil health, and human safety.