Polystyrene microplastics promote intestinal colonization of Aeromonas veronii through inducing intestinal microbiota dysbiosis

Size-dependent ecotoxicological impacts of tire wear particles on zebrafish physiology and gut microbiota: Implications for aquatic ecosystem health

The ecological impact of tire wear particles (TWP), a significant source of microplastics pollution, is increasingly concerning, especially given their potential effects on the health of aquatic ecosystems. This study investigates the size-dependent ecotoxicological responses of zebrafish (Danio rerio) to TWP exposure, focusing on physiological, metabolic, and microbial community impacts over a 15-day exposure period followed by a 15-day excretion period. Through integrated analysis of gut microbiome composition, liver transcriptomics, and host physiological markers, we found that smaller TWP particles (< 120 μm) induced oxidative stress, evidenced by increased SOD and MDA levels, and inhibited growth by reducing body mass and gut length. In contrast, larger TWP particles (250-380 μm) caused more substantial disruptions in lipid and xenobiotic metabolic pathways, as shown by significant downregulation of key metabolic genes (acads, cpt2_1, hadhaa), and alterations in the gut microbiome, including the enrichment of pathogenic genera, such as Enterococcus and Fusobacterium, while depleting beneficial microbes like Acinetobacter and Methyloversatilis. These microbiome shifts led to a more complex and potentially pathogenic gut microbiome. Notably, zebrafish displayed adaptive resilience during the excretion period, with significant recovery in body mass and microbial composition, emphasizing the adaptive capacity of aquatic organisms to pollutants. Our findings underscore the broader ecological risks posed by TWP, the pivotal role of gut microbiota in host resilience to pollutants, and the need for comprehensive management strategies addressing emerging contaminants in aquatic ecosystems.

Autoinducer-2 signaling promotes intestinal colonization of Aeromonas veronii and induces cell apoptosis in loach (Misgurnus anguillicaudatus)

Quorum sensing systems, particularly autoinducer-2 (AI-2) signaling, have significant effects on bacterial colonization and virulence. However, how they affect intestinal colonization by pathogens and subsequent host immune responses remains unclear. Here, we investigated the influence of AI-2 signaling on the intestinal colonization ability of Aeromonas veronii Z12 and the host's immune response. We found that AI-2 signaling promoted the colonization of A. veronii to the intestine of loach (Misgurnus anguillicaudatus) and caused severe intestinal damage, while D-ribose, an AI-2 signaling inhibitor, effectively inhibited the colonization of A. veronii. Transcriptomic sequencing elucidated the molecular mechanism of this damage, revealing upregulation of p53 pathway genes associated with apoptosis. Furthermore, intestinal microbiota dysbiosis induced by A. veronii colonization was associated with host cell apoptosis, leading to nitrite accumulation, which increased intracellular reactive oxygen species (ROS) levels, which activated the p53 pathway, and induction of cell apoptosis. These findings provide insights into the interaction among bacterial quorum sensing, intestinal microbiota, and the host immune response, which highlight potential therapeutic targets for mitigating bacterial-induced intestinal damage.IMPORTANCEThe intestinal colonization of pathogens regulated by autoinducer-2 (AI-2) signaling and its induced host response have not been fully characterized. Here, we revealed the effect of AI-2 on intestinal colonization of Aeromonas veronii and its induced cell apoptosis in loach. Our study demonstrated that the deficiency of AI-2 significantly reduced A. veronii colonization in the loach intestine and mitigated the tissue damage. Additionally, A. veronii colonization induced significant upregulation of p53 pathway genes and proteins, indicating a key role of AI-2 signaling in host responses. Understanding these mechanisms not only helps to elucidate the pathogenicity of A. veronii but also may provide broader insights into the pathogenic mechanisms of other pathogens, thus revealing general principles of pathogen-host interactions across different models. Furthermore, we found that A. veronii colonization led to intestinal microbiota dysbiosis, notably an increase in the abundance of Hypomicrobium sp., which was associated with nitrite accumulation, elevating reactive oxygen species levels, activating the p53 pathway, and inducing cell apoptosis. These findings provide important insights into the complex mechanisms of AI-2 signaling in bacterial-host interactions. Additionally, the regulatory role of AI-2 signaling may have potential clinical applications as an intervention strategy, offering new directions for developing treatments against intestinal infections.

Microplastics colonized by Hafnia paralvei through biofilm formation regulated by c-di-GMP and cAMP promote its spread in water

Microplastics (MPs) colonized by pathogens pose significant risks to the environment and health of animals and humans, however, the strategies for pathogens colonization in MPs and the effects of its colonization on spread of pathogens have not been fully characterized. Here, we investigated the biofilm formation mechanism regulated by c-di-GMP in Hafnia paralvei Z11, and determined the effect of MPs colonized by H. paralvei Z11 on the spread of strain Z11. Overexpression of yhjH, a c-di-GMP phosphodiesterase gene, attenuated intracellular c-di-GMP level in strain Z11, leading to an increase in biofilm dispersal and a decrease in biofilm formation. Meanwhile, the decline of c-di-GMP inhibited the expression of cAMP phosphodiesterase genes, increasing the cAMP content and promoting bacterial motility, that was responsible for the increase of biofilm dispersal. Furthermore, the formation of biofilms by strain Z11 on MPs promotes its colonization, which contributes to its vertical and horizontal spread in water after colonizing polyvinyl chloride-MPs and polypropylene-MPs, respectively. Therefore, this study reveals, for the first time, MPs colonized by H. paralvei Z11 through biofilms regulated by crosstalk between c-di GMP and cAMP promote the spread of strain Z11 in water, which expands the understanding of colonization strategy of pathogens on MPs and its risk on spread of pathogens.

The role of gut microbiota in MP/NP-induced toxicity

Microplastics (MPs) and nanoplastics (NPs) are globally recognized as emerging environmental pollutants in various environmental media, posing potential threats to ecosystems and human health. MPs/NPs are unavoidably ingested by humans, mainly through contaminated food and drinks, impairing the gastrointestinal ecology and seriously impacting the human body. The specific role of gut microbiota in the gastrointestinal tract upon MP/NP exposure remains unknown. Given the importance of gut microbiota in metabolism, immunity, and homeostasis, this review aims to enhance our current understanding of the role of gut microbiota in MP/NP-induced toxicity. First, it discusses human exposure to MPs/NPs through the diet and MP/NP-induced adverse effects on the respiratory, digestive, neural, urinary, reproductive, and immune systems. Second, it elucidates the complex interactions between the gut microbiota and MPs/NPs. MPs/NPs can disrupt gut microbiota homeostasis, while the gut microbiota can degrade MPs/NPs. Third, it reveals the role of the gut microbiota in MP/NP-mediated systematic toxicity. MPs/NPs cause direct intestinal toxicity and indirect toxicity in other organs via regulating the gut-brain, gut-liver, and gut-lung axes. Finally, novel approaches such as dietary interventions, prebiotics, probiotics, polyphenols, engineered bacteria, microalgae, and micro/nanorobots are recommended to reduce MP/NP toxicity in humans. Overall, this review provides a theoretical basis for targeting the gut microbiota to study MP/NP toxicity and develop novel strategies for its mitigation.