In vivo environmental metabolomic profiling via a novel microextraction fiber unravels sublethal effects of environmental norfloxacin in gut bacteria.

Emerging contaminants (ECs), especially antibiotics, have significantly polluted the environment and threaten the living circumstance of organisms. Environmental metabolomic has emerged to investigate the sublethal effects of ECs. However, lacking noninvasive and real-time sample pretreatment techniques restricts its development in environmental toxicology. Hence, in this study, a real-time and in vivo untargeted analytical technique towards microbial endogenous metabolites was developed via a novel composite solid-phase microextraction (SPME) fiber of ZIF-67 and polystyrene to realize the high-coverage capture of living gut microbial metabolites. To reveal the exposure risks of typical antibiotic - norfloxacin (NFX) to gut bacteria, four representative bacteria were exposed to NFX at environmentally relevant levels. Using the proposed SPME fiber, 70 metabolites were identified to obtain an apparent metabolic separation feature between control and NFX-treated (10 ng/mL) microbial groups, which revealed that the low environmental relevant concentration of NFX would affect normal metabolism of gut bacteria. Additionally, NFX exhibited species-specific toxic effects on microbial growth, especially Escherichia coli displaying a distinct dose-dependent trend. Antioxidative enzymatic activities results demonstrated that beneficial bacteria maintained the state of oxidative stress while symbiotic bacteria suffered from oxidative stress injury under NFX contamination, further corroborating its impact on human intestinal health. This study highlights the suitability of in vivo SPME in the field of metabolite extraction and simultaneously possesses a brilliant application foreground in the environmental metabolomics.