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Polystyrene-degrading bacteria modulate host stress and toxicity responses to microplastic exposure in Caenorhabditis elegans
Summary
Scientists studied how gut bacteria affect the health impacts of microplastics (tiny plastic particles) using lab worms as a model. They found that different types of plastic-eating bacteria in the gut can either make microplastic exposure more harmful or help protect against it. This research suggests that the specific mix of bacteria in our intestines might influence how dangerous microplastics are to our health.
Microplastic exposure is an emerging health risk. Host-associated plastic-degrading commensal bacteria can directly interact with microplastic particles and alter them physically and chemically, thereby potentially modulating microplastic toxicity. Despite numerous reports of plastic-degrading bacteria isolated from host intestines, how these interactions affect host physiology remains unclear. Here, we compared two polystyrene-degrading bacteria-Enterobacter hormaechei LG3 and Bacillus amyloliquefaciens SCGB1-in Caenorhabditis elegans exposed to laboratory-manufactured 1-μm polystyrene microspheres (Mi-PS). LG3-fed worms showed dose-dependent physiological impairment in response to Mi-PS, whereas SCGB1-fed worms exhibited attenuated or negligible impairment. The strains interacted with Mi-PS via distinct physiological and metabolic responses, reflected by differences in biofilm formation, particle attachment, and metabolite profiles. These strain-specific differences were confirmed to directly influence host outcomes. Under identical exposure conditions (10 mg/L, 50 h), LG3-fed worms accumulated more Mi-PS particles in the gut than SCGB1-fed worms (n = 48; mean ± SD, 3.28 ± 4.22 vs 0.63 ± 1.03 particles per worm). A transcriptome-guided validation framework provided mechanistic clues to strain-specific microplastic interactions. LG3-associated impairment coincided with the formation of oxidized Mi-PS particles, production of oxidized styrene intermediates, and microparticle-driven changes in bacterial cell properties, including activation of the lipopolysaccharide biosynthesis pathway. In contrast, SCGB1-associated attenuation was consistent with isobutyrate/isovalerate-mediated modulation of host DAF signaling. Collectively, these results link bacteria-microplastic interactions to host outcomes and offer actionable insight for assessing and mitigating microplastic-related health risks.
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