Sub-chronically exposing zebrafish to environmental levels of methomyl induces dysbiosis and dysfunction of the gut microbiota

The widespread use of carbamate pesticides has led to numerous environmental and health concerns, including water contamination and perturbation of endocrine homeostasis among organisms. However, there remains a paucity of research elucidating the specific effects of methomyl on gut microbial composition and physiological functions. This study aimed to investigate the intricate relationship between changes in zebrafish bacterial communities and intestinal function after 56 days of sub-chronic methomyl exposure at environmentally relevant concentrations (0, 0.05, 0.10, and 0.20 mg/L). Our findings reveal significant methomyl-induced morphological changes in zebrafish intestines, characterized by villi shortening and breakage. Notably, methomyl exposure down-regulated nutrient and energy metabolism, and drug metabolism at 0.05-0.10 mg/L, while up-regulating cortisol, inflammation-related genes, and apoptotic markers at 0.20 mg/L. These manifestations indicate physiological stress imposition and disruption of gut microbiota equilibrium, impacting metabolic processes and instigating low-grade inflammatory responses and apoptotic cascades. Importantly, changes in intestinal function significantly correlated with shifts in specific bacterial taxa abundance, including Shewanella, Rubrobacter, Acinetobacter, Bacillus, Luteolibacter, Nocardia, Defluviimonas, and Bacteroides genus. In summary, our study underscores the potential adverse effects of environmental methomyl exposure on aquatic organisms, emphasizing the necessity for further research to mitigate its repercussions on environmental health and ecosystem stability.