Biotransformation of seafood arsenic by intestinal microbiota: A critical review on ecotoxicological and health risk implications

Arsenic (As) is a toxic element widely distributed in the marine environment, making seafood the primary dietary route of human exposure. It is present in diverse chemical forms, including low-toxicity organic species, such as arsenobetaine (AsB) and arsenosugars (AsSugars), and high-toxicity inorganic arsenic (iAs). While the human gut microbiota is known to play a crucial role in arsenic metabolism, a systematic summary of these complex biotransformations, particularly for organic species, is currently lacking. This review addresses this knowledge gap by providing a comprehensive overview of the established research on microbe-mediated arsenic metabolism. Our work summarizes the principal microbial pathways for inorganic arsenic, including oxidation, reduction, and methylation, which modulate its toxicity. Furthermore, we synthesize the emerging body of research on the metabolism of major organic arsenicals, covering the degradation of AsSugars, the biotransformation of arsenolipids (AsLipids), and the initial findings on the metabolic fate of AsB. The key functional bacterial genera implicated in these processes are also identified. We conclude that a thorough understanding of these intricate microbe-arsenic interactions is essential for improving ecotoxicological models, accurately assessing health risks associated with seafood consumption, and establishing robust, evidence-based public health guidelines.