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Temporal dynamics of lake microbiota under nanoplastic and enrofloxacin stress
Summary
Researchers exposed lake microbiota to polystyrene nanoplastics and the antibiotic enrofloxacin over 14 days to track their combined effects on bacterial abundance, respiration, community physiology, and taxonomy. By day 14, community structure diverged significantly under combined stress — alpha-diversity remained depressed only under high antibiotic concentrations with nanoplastics present — demonstrating that nanoplastic and antibiotic co-exposure produces distinct and time-evolving microbial community shifts.
Nanoplastics (NPs) and antibiotics co-occur in freshwaters, yet their time-resolved, joint impacts on bacterial communities remain poorly constrained. We exposed lake microbiota to polystyrene NPs (∼420 nm; 10-10 particles L) and enrofloxacin (ENR; 10 or 100 ng L), tracking abundance, per-cell respiration, community-level physiological profiles (CLPP), and taxonomy for 14 days. By day 7, both stressors reduced abundance, with stronger ENR effects; CLPP was depressed mainly by ENR, whereas per-cell respiration rose in several NP × ENR combinations, and substrate use shifted transiently from complex carbons toward simpler substrates (notably amines). By day 14, population-level responses attenuated, but community structure diverged: α-diversity remained depressed only under high ENR with NPs, β-diversity resolved into three assemblages (elevated Sporichthyaceae and Comamonadaceae; reduced Burkholderiaceae and Verrucomicrobiaceae), and Actinobacteriota remained dominant. A Mantel test indicated that taxonomic restructuring increasingly explained physiological profiles at day 14. A complementary fate experiment showed dissolved ENR declined strongly over days, faster in bacteria-present (unfiltered) water and further with NPs, with several NP-amended, unfiltered treatments approaching the analytical LOD; a 4 h assay detected no treatment differences, indicating negligible immediate photolysis or rapid sorption. Together, results show that biological sinks, augmented by NPs over multi-day timescales, govern ENR removal, explaining the time-dependent decoupling between early physiological stress and later partial functional recovery alongside persistent compositional shifts. Overall, NP-antibiotic interactions were time-dependent and sometimes antagonistic at the population level, yet produced lasting community reassembly. Time-resolved, multi-level assessments are essential for ecological risk appraisal of contaminant mixtures in freshwater microbiomes.
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