μEvaluation of microcystin-LR absorption using an in vivo intestine model and its effect on zebrafish intestine

Area of Science:

• Environmental Toxicology
• Microbiology
• Aquatic Ecology

Background:

• Microcystin-LR (MC-LR) is a potent toxin causing organ dysfunction, particularly gastrointestinal issues.
• Limited research exists on MC-LR's impact on gut microbiota composition.
• Understanding MC-LR's effects on fish gut health is crucial for aquatic ecosystem management.

Purpose of the Study:

• To investigate the effects of MC-LR exposure on zebrafish gut microbiota composition.
• To characterize the phylogenetic and taxonomic changes in bacterial communities following MC-LR treatment.
• To explore the relationship between MC-LR exposure, gut microbiota, and stress-related gene expression.

Main Methods:

• Ex vivo everted gut sac model and zebrafish intestine accumulation studies to assess MC-LR absorption.
• 16S rRNA pyrosequencing to analyze gut bacterial community structure in zebrafish.
• Dose-response experiments with varying MC-LR concentrations (0, 1, 5, 20 μg/L) over 30 days.
• Analysis of Oatp2b1 expression and gut stress enzyme activities.

Main Results:

• MC-LR absorption and accumulation in zebrafish intestine showed a dose-dependent pattern.
• No significant changes in alpha and beta diversity of gut microbiota were observed, suggesting a core microbiota.
• High-dose MC-LR (20 μg/L) significantly altered the characteristics of abundant bacterial phylotypes.
• Changes included an increase in Actinobacteria, Lactobacillus, and opportunistic pathogens, alongside potential probiotic resistance.

Conclusions:

• MC-LR exposure can significantly alter zebrafish gut microbiota composition, even with a stable core.
• High MC-LR concentrations elevate the risk of opportunistic pathogen invasion in the gut.
• The findings highlight the complex interactions between microcystins, gut microbial communities, and host health in aquatic organisms.