Farkas Michael H, Berry James O, Aga Diana S
Department of Biological Sciences, University at Buffalo, Buffalo, New York 14260, USA.
Environ Sci Technol. 2007 Feb 15;41(4):1450-6. doi: 10.1021/es061651j.
Soil contamination with nonmetabolized antibiotics is an emerging environmental concern, especially on agricultural croplands that receive animal manure as fertilizer. In this study, phytotoxicity of chlortetracycline (CTC) antibiotics on pinto beans (Phaseolus vulgaris) and maize (Zea mays) was investigated under controlled conditions. When grown in CTC-treated soil, a significant increase in the activities of the plant stress proteins glutathione S-transferases (GST) and peroxidases (POX) were observed in maize plants, but not in pinto beans. In vitro conjugation reactions demonstrated that the induced GST in maize catalyzed the conjugation of glutathione (GSH) with CTC, producing stable conjugates that were structurally characterized using liquid chromatography/mass spectrometry. The antibiotic-induced GST produced CTC-glutathione conjugate at relative concentrations 2-fold higher than that produced by constitutively expressed GST extracted from untreated maize. On the other hand, GST extracted from pinto beans (both treated and untreated) did not efficiently catalyze glutathione conjugation with CTC. These results suggest that maize is able to detoxify chlortetracycline via the glutathione pathway, whereas pinto beans cannot. This may explain the observed stunted growth of pinto beans after antibiotic treatment. This study demonstrates the importance of plant uptake in determining the fate of antibiotics in soil and their potential phytotoxicity to susceptible plants.
未代谢抗生素对土壤的污染是一个新出现的环境问题，尤其在使用动物粪便作为肥料的农田中。在本研究中，在可控条件下研究了金霉素（CTC）抗生素对菜豆（Phaseolus vulgaris）和玉米（Zea mays）的植物毒性。当种植在经CTC处理的土壤中时，在玉米植株中观察到植物应激蛋白谷胱甘肽S-转移酶（GST）和过氧化物酶（POX）的活性显著增加，但在菜豆中未观察到。体外偶联反应表明，玉米中诱导产生的GST催化谷胱甘肽（GSH）与CTC偶联，生成稳定的偶联物，使用液相色谱/质谱对其结构进行了表征。抗生素诱导产生的GST产生的CTC-谷胱甘肽偶联物的相对浓度比从未经处理的玉米中提取的组成型表达的GST产生的偶联物高2倍。另一方面，从菜豆（无论处理与否）中提取的GST不能有效地催化谷胱甘肽与CTC的偶联。这些结果表明，玉米能够通过谷胱甘肽途径对金霉素进行解毒，而菜豆则不能。这可能解释了抗生素处理后菜豆生长发育迟缓的现象。本研究证明了植物吸收在决定土壤中抗生素的归宿及其对敏感植物潜在的植物毒性方面的重要性。
