Antibiotics and antibiotic resistance genes (ARGs) are emerging contaminants of concern in large-river sediments, yet their spatial covariation across dam-regulated river systems remains poorly understood. To address this question, surface sediments were collected along the main stem of the Yangtze River, covering the upstream reach, the Three Gorges Reservoir (TGR), the middle reach, and the downstream reach. Of the 44 target antibiotics, 35 were detected. Metagenomic analysis of 15 samples with useable sequencing datasets identified 828 putative ARG subtypes, among which 23 representative subtypes were selected for detailed spatial comparison. Tetracyclines accounted for more than 90% of the total antibiotic burden, with mean concentrations decreasing from 82.97 ng/g upstream to 70.81 ng/g in the TGR, and 49.22 ng/g downstream. In contrast, the summed abundance of the 23 selected ARGs was higher downstream (68,867 RPKM) than upstream (48,377 RPKM), demonstrating incomplete spatial concordance between antibiotic residues and the sediment resistome. Exploratory multivariate analyses indicated that ARGs variation was jointly associated with sediment properties, antibiotic residues, microbial communities, and MGEs. The PLS-PM showed positive direct path coefficients from antibiotics (β = 0.390), MGEs (β = 0.334), and sediment properties (β = 0.306) to ARGs. Pseudomonadota- and Nitrospirota-affiliated metagenome-assembled genomes were identified as potential ARGs hosts. Positive associations between ARGs and mobile genetic elements suggested elevated genetic mobility potential within the sediment resistome. Risk assessment identified tetracycline as the principal antibiotic-related ecological concern, with a maximum hazard quotient of 18.9 in the TGR, whereas the evaluated ARGs remained within the lowest potential human-health risk rank. These findings demonstrate contrasting spatial patterns of antibiotics and ARGs along the Yangtze River and identify sediment properties, microbial communities, and genetic mobility potential as important correlates of ARGs variation.
Zearalenone (ZEN) is mycoestrogen that is produced by Fusarium fungi. Despite the increasing recognition that humans and wildlife are typically exposed to complex mixtures of endocrine-disrupting chemicals rather than individual compounds, the interactions between naturally occurring xenoestrogens and/or phytoestrogens remain poorly understood and mostly evaluated based on in vitro experiments. In the current study, the combined estrogenic effects of ZEN with phytoestrogens (daidzein and genistein), pesticide-related compounds (glyphosate and aminomethylphosphonic acid), plastic-derived xenoestrogens (bisphenol A and S), its own conjugated metabolites (ZEN-14- O -sulfate and ZEN-14- O -glucuronide), and other mycoestrogens (alternariol and alternariol-3- O -sulfate) were examined applying the Tg( vtg1 :mCherry) transgenic zebrafish embryo model. Genistein, glyphosate, and bisphenols markedly increased ZEN-induced estrogenicity, even at nanomolar and/or low micromolar levels where they did not show estrogenic impacts alone in the model used. However, ZEN-14- O -sulfate and alternariol-3- O -sulfate reduced the ZEN-induced response, showing their most dominant actions at nanomolar concentrations. Interestingly, ZEN-14- O -sulfate can also decrease the impact of 17β-estradiol while alternariol-3- O -sulfate enhanced it, suggesting complex modulatory ability of the latter metabolite. Response-additivity analysis identified significant supra-additivity with genistein (0.75 μM), bisphenol A (0.25 μM and 0.75 μM), and bisphenol S (0.75 μM); while sub-additivity was noticed with aminomethylphosphonic acid (0.25 μM) and alternariol-3- O -sulfate (all concentrations tested).
With the intensification of livestock production, livestock manure has become a major pathway for the introduction of antibiotics and microplastics into agricultural soils. However, the relative contributions of manure organic fertilizer, antibiotics, and microplastics to soil microbial communities remain poorly resolved. In this study, ten pastoral farmland fields surrounding a large-scale cattle farm in northwestern China were investigated. Fecal sterol molecular markers were used to characterize the relative intensity of cattle manure input, while regionally prevalent antibiotics and soil microplastics were quantified and related to microbial community structure. The results showed that stigmastanol concentrations were significantly positively correlated with soil electrical conductivity, total nitrogen, organic matter, and available phosphorus, confirming the reliability of stigmastanol as a proxy for cattle manure input. The summed concentration of the 12 target antibiotics (Σ12 antibiotics) was not significantly associated with the manure-input gradient; only pefloxacin, ciprofloxacin, and enrofloxacin were significantly positively correlated with stigmastanol, whereas tetracyclines showed no significant association with the manure proxy. Microplastics were predominantly fine particles (<50 μm), while variation in polymer composition indicated contributions from both manure-associated and non-manure sources. Principal coordinate analysis revealed that sites with higher manure input clustered independently along the PCo1 axis (explaining 45.6% of the variation). In single-predictor distance-based redundancy analysis, stigmastanol was the strongest measured correlate of microbial community structure (adjusted R2 = 0.394, p = 0.003). Variance partitioning further showed substantial overlap among the explanatory fractions associated with manure input, the selected antibiotic proxy, and microplastic abundance: the marginal association of pefloxacin was largely shared with the manure-input proxy, whereas the unique fraction associated with microplastics remained exploratory because its single-predictor model was not significant. This study establishes the predominant role of manure input in shaping the structural differentiation of soil microbial communities in pastoral farmland, rules out an independent community-level effect of antibiotics at current residual concentrations, and provides clear research hypotheses and priorities for subsequent controlled experiments investigating manure–antibiotic–microplastic interactions.
Zearalenone (ZEN) is mycoestrogen that is produced by Fusarium fungi. Despite the increasing recognition that humans and wildlife are typically exposed to complex mixtures of endocrine-disrupting chemicals rather than individual compounds, the interactions between naturally occurring xenoestrogens and/or phytoestrogens remain poorly understood and mostly evaluated based on in vitro experiments. In the current study, the combined estrogenic effects of ZEN with phytoestrogens (daidzein and genistein), pesticide-related compounds (glyphosate and aminomethylphosphonic acid), plastic-derived xenoestrogens (bisphenol A and S), its own conjugated metabolites (ZEN-14-O-sulfate and ZEN-14-O-glucuronide), and other mycoestrogens (alternariol and alternariol-3-O-sulfate) were examined applying the Tg(vtg1:mCherry) transgenic zebrafish embryo model. Genistein, glyphosate, and bisphenols markedly increased ZEN-induced estrogenicity, even at nanomolar and/or low micromolar levels where they did not show estrogenic impacts alone in the model used. However, ZEN-14-O-sulfate and alternariol-3-O-sulfate reduced the ZEN-induced response, showing their most dominant actions at nanomolar concentrations. Interestingly, ZEN-14-O-sulfate can also decrease the impact of 17β-estradiol while alternariol-3-O-sulfate enhanced it, suggesting complex modulatory ability of the latter metabolite. Response-additivity analysis identified significant supra-additivity with genistein (0.75 μM), bisphenol A (0.25 μM and 0.75 μM), and bisphenol S (0.75 μM); while sub-additivity was noticed with aminomethylphosphonic acid (0.25 μM) and alternariol-3-O-sulfate (all concentrations tested).
