摘要
      随着兽医抗生素的使用越来越多，喹诺酮类抗生素可能在牲畜粪便堆肥后进入农田系统。然而，抗生素对作物的植物毒性机制尚不清楚。在本研究中，研究了水稻幼苗对三种典型喹诺酮类抗生素的氧化反应及其潜在机制。左氧氟沙星、恩诺沙星和诺氟沙星处理的生物浓缩因子值分别为1.47、0.55和0.23。对水稻幼苗的抑制作用依次为左氧氟沙星>恩诺沙星>诺氟沙星，这可能是由于左氧氟沙星的高摄取所致。H2O2水平、MDA含量和离子泄漏率显著升高（p<0.05），并观察到细胞浆裂解，表明抗生素可引起细胞膜脂质过氧化，破坏细胞膜结构。抗氧化酶活性（超氧化物歧化酶、过氧化氢酶和过氧化物酶）随抗生素浓度的变化而变化。综合生物标志物反应分析表明，左氧氟沙星对水稻幼苗造成的氧化应激最大。转录组学分析鉴定了5880个差异表达基因，这些基因被注释为20种生物功能；丰度最大的是细胞和代谢过程、细胞部分、膜部分和细胞器；SOD和CAT相关基因表达上调。叶层微生物群落的丰富度和多样性显著下降（p<0.05），微生物组在门和属水平上发生了变化。H2O2水平与叶际微生物群落的变化相关。抗生素抗性基因（ARGs）和可移动遗传元件的数量减少，而它们的丰度增加。总之，恩诺沙星暴露不仅会影响微生物群落，还可能影响微生物携带的ARGs。MGE和ARGs的相对丰度显著正相关（R2=0.760，p=0.0148），表明MGE可以显著促进ARGs传播。
Abstract
With the increasing use of veterinary antibiotics, quinolone antibiotics may enter farmland systems after livestock manure has been composted. However, the phytotoxicity mechanism of antibiotics in crops is still unclear. In this study, the oxidative responses of rice (Oryza sativa L.) seedlings to three typical quinolone antibiotics and their underlying mechanisms were investigated. The bioconcentration factor values were 1.47, 0.55, and 0.23 in the levofloxacin, enrofloxacin and norfloxacin treatment, respectively. The inhibitory effects on rice seedlings were in the order of levofloxacin > enrofloxacin > norfloxacin, which may be due to the high uptake of levofloxacin. The H2O2 level, MDA content, and ion leakage rate increased significantly (p < 0.05), and cell plasmolysis was observed, showing that antibiotics can cause membrane lipid peroxidation and damage the cell membrane structure. Antioxidant enzyme activities (superoxide dismutase, catalase, and peroxidase) changed with the antibiotic concentration. Integrated biomarker response analysis showed that levofloxacin caused the greatest oxidative stress in rice seedlings. Transcriptomic analysis identified 5880 differentially expressed genes, and these were annotated as 20 biological functions; the greatest abundances were cellular and metabolic processes, cell part, and membrane part and organelle; SOD and CAT related genes were up-regulated. The richness and diversity of the phyllosphere microbial community decreased significantly (p < 0.05) and the microbiome changed at the phylum and genus levels. The H2O2 level was correlated with changes in phyllosphere microbial communities. The number of antibiotic resistance genes (ARGs) and mobile genetic elements decreased, while their abundance increased. In conclusion, enrofloxacin exposure not only affects the microbial community but may also affect the ARGs carried by microbes. The relative abundance of MGEs and ARGs was significantly positively correlated (R2 = 0.760, p = 0.0148), indicating that MGEs can significantly promote the spread of ARGs.

https://www.sciencedirect.com/science/article/abs/pii/S0048969723001596