Microalgae in the enrichment and spread of antibiotic resistance genes in watersheds: a review

The widespread use of antibiotics has led to antimicrobial resistance (AMR), which has become one of the most serious threats to global health. The coexistence of microalgae and bacteria enhances the abundance and transmission of antibiotic resistance genes (ARGs), thereby increasing their environmental hazard. This study summarizes the roles of microalgae in the enrichment and spread of ARGs. First, the characteristics of microalgae and the features of the phycosphere microenvironment are systematically reviewed. Second, the role and mechanisms of ARG enrichment and spread mediated by microalgae are discussed. As the core innovation in this article, scattered research evidence is integrated to comprehensively elucidate the environmental drivers and underlying mechanisms that render the phycosphere a critical niche for the proliferation and transmission of ARGs. Furthermore, the contaminants influencing the transfer of ARGs within the phycosphere further confirm the elevated ARG risks induced by microalgae in watersheds. However, research on ARGs in the phycosphere remains in its infancy. Research challenges and prospects related to mechanism, transmedia spread, and adaptive evolution are also highlighted. This timely synthesis consolidates fragmented studies, clarifies the pathways of microalgae-mediated ARG transmission, and provides the scientific community with a clearer understanding of this hidden environmental process. It also offers a scientific basis for assessing and intervening in the diffusion of ARGs in watersheds.