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Published on: December 27, 2016
Combined effects of ciprofloxacin and microplastics on alpine spring water microbiota: evidence from glacier-fed
Domenica Mosca Angelucci1, Federica Piergiacomo2, Enrica Donati3
1Water Research Institute, National Research Council (CNR-IRSA), Rome, Italy.
Introduction:
Emerging contaminants such as microplastics (MPs) and antibiotics pose increasing environmental and public health risks due to their persistence and incomplete removal by wastewater treatment processes. MPs can act as vectors for antibiotics, facilitating their environmental spreading and supporting biofilm formation, which can enhance horizontal gene transfer and antibiotic resistance. This study investigates the combined effects of ciprofloxacin (CIP) and polyethylene terephthalate (PET) MPs on microbiota in alpine spring water (SW) sourced from a rock glacier.
Methods:
Four experimental scenarios (Control, CIP, PET, CIP + PET) were established to assess the sorption dynamics of CIP onto PET particles and the consequent microbial responses. A multidisciplinary analytical approach combining ultra-performance liquid chromatography, microscopy, quantitative PCR, and metabarcoding was applied.
Results:
CIP exhibited progressive sorption onto PET, accompanied by a time-dependent increase in biofilm formation, most pronounced in the CIP + PET condition. qPCR revealed elevated copy numbers of resistance genes qnrA and qnrB in CIP + PET, suggesting synergistic effects between antibiotics and MPs in promoting resistance. CIP was the dominant driver of microbial compositional shifts, favoring known CIP-degrading taxa. A shared core microbiome of 216 amplicon sequence variants was detected across all conditions, but specific taxa were differentially enriched under varying exposures. The combined CIP + PET test induced the strongest community shifts, while CIP alone shared fewer taxa with controls, indicating selective pressure for resistant microorganisms like Achromobacter. PET MPs also shaped distinct microbial assemblages, possibly by offering niches favoring biofilm-associated genera such as Luteolibacter. Biodiversity metrics showed highest richness and evenness in CIP-free conditions (Control and PET), while CIP significantly reduced alpha diversity, favoring resistant taxa, as confirmed by NMDS and lower Shannon and Simpson indices. Effects of MPs were still noticeable.
Conclusion:
These findings demonstrate the disruptive effects of CIP on alpine freshwater microbial communities and highlight the additional, though more moderate, influence of MPs. The combined presence of MPs and antibiotics may exacerbate resistance spreading by enhancing persistence and providing favorable conditions for resistant biofilms. A mechanistic understanding of these interactions is essential for accurate risk assessment and the development of effective mitigation strategies in alpine and other vulnerable freshwater ecosystems.
Insights
Microplastics (MPs) and ciprofloxacin (CIP) disrupt alpine freshwater microbes, with MPs potentially enhancing antibiotic resistance. Understanding these interactions is crucial for ecosystem protection.
Area of Science:
- Environmental Science
- Microbiology
- Ecotoxicology
Background:
- Emerging contaminants like microplastics (MPs) and antibiotics (e.g., ciprofloxacin - CIP) pose significant environmental and health risks.
- MPs can act as vectors for antibiotics, promoting biofilm formation and potentially enhancing antibiotic resistance gene transfer.
- Alpine freshwater ecosystems are vulnerable to these combined contaminant pressures.
Purpose of the Study:
- To investigate the combined effects of ciprofloxacin (CIP) and polyethylene terephthalate (PET) microplastics on the microbial communities in alpine spring water.
- To assess the sorption dynamics of CIP onto PET MPs and the resulting microbial responses.
- To understand the synergistic or antagonistic interactions between CIP and PET MPs on microbial structure and function.
Main Methods:
- Experimental setup with four scenarios: Control, CIP, PET, and CIP + PET.
- Analysis of CIP sorption onto PET MPs.
- Multidisciplinary approach including UPLC, microscopy, qPCR, and 16S rRNA gene metabarcoding for microbial analysis.
Main Results:
- CIP sorbed onto PET MPs, increasing over time and promoting biofilm formation, especially in the combined CIP+PET condition.
- Elevated antibiotic resistance genes (qnrA, qnrB) were observed in the CIP+PET group, indicating synergistic effects.
- CIP significantly altered microbial community composition, favoring CIP-degrading taxa and reducing alpha diversity, while PET MPs influenced specific biofilm-associated genera.
Conclusions:
- Ciprofloxacin significantly disrupts alpine freshwater microbial communities, with microplastics exerting a moderate but noticeable influence.
- The combined presence of MPs and antibiotics may accelerate antibiotic resistance spread by enhancing persistence and promoting resistant biofilms.
- Further research into these interactions is vital for risk assessment and developing mitigation strategies for vulnerable freshwater ecosystems.
