Antibiotics and microbial community-induced antibiotic-resistant genes distribution in soil and sediment in the eastern coastline of China.

The health risk of antibiotic-resistant genes (ARGs) has been a global concern, while the report on occurrence and prevalence of ARGs in coastal zone is relatively scarce. This study investigated typical ARGs in soil and sediment in coastal line of eastern China and assessed its relationship with antibiotics and heavy metals as well as microbial community. Results showed that eight ARGs were all detected in the samples, and ß-lactam resistance gene blaTEM reached the highest absolute abundance (6.28 × 107 ~ 6.48 × 108 copies/g) and relative abundance (2.3 × 10-2 copies/16S rRNA) among samples. Amoxicillin and tetracycline were most frequently detected with the average concentration of 2.28 µg/kg and 3.48 µg/kg, respectively. Cr and Zn were found to be most abundant heavy metals with average value of 82.1 and 59.1 mg/kg, respectively. Proteobacteria, Campilobacterota, Bacteroidota, and Firmicutes were dominant phyla in most samples, while bacterial community varied significantly among samples. Redundancy analyses (RDA) showed that microbial community and antibiotics (amoxicillin and tetracycline) were driving factors of ARGs distribution, while heavy metals were not significantly correlated with ARGs. This study is helpful to understand the fate of ARGs in coastal zone.

Combined toxicity of polystyrene microplastics and sulfamethoxazole on zebrafish embryos.

Despite extensive investigation on the toxicity of microplastics (MPs), an emerging global concern, little is known about the combined toxicity of MPs and co-occurring pollutants in aquatic environments. In this study, the combined toxicity of polystyrene MPs and sulfamethoxazole (SMZ) antibiotics was explored in zebrafish embryos in terms of the developmental, physiological, and endocrine toxicities. Exposure to PS and SMZ induced mortality (rate: 25.0 ± 7.5%) and malformation (rate: 20~35%) at multiple regions and stages of zebrafish development. Physiological toxicity was also induced as shown by the significant decrease in fetal movement (by 31.1~37.0%) and swimming frequency (by 26.9~36.8%) and the increase in heartbeat rate (by 19.0~20.9%). Finally, PS and SMZ exposure also induced extensive endocrine toxicities in zebrafish as confirmed by increases in various biomarkers including vitellogenin, 17ß-estradiol, testosterone, and triiodothyronine. The combination index showed that antagonistic effects were present between PS and SMZ toxicity, which slightly decreased their combined toxicity. This study aims to further understand the combined toxicity of MPs and co-occurring pollutants in aquatic environments.