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[Objective] Antibiotics as emerging pollutants have aroused wide concern. In view of the shortage of effective tetracycline-degrading strains, this study aims to screen and identify the strains for tetracycline degradation, analyze degradation properties and type, pinpoint the localization of active substances for bio-degradation, and evaluate the physiological toxicity of degradation products. [Methods] Tetracycline was used as the sole carbon source to screen out the target strain from tetracycline-contaminated pig sludge. The strain was identified based on colony morphology, physiological and biochemical characteristics, scanning electron microscopy images, and the 16S rRNA gene sequence. Different carbon sources, pH, and removal kinetics were employed to characterize the degradation process of the strain. Different components of the strain were extracted to determine the degradation type of tetracycline by the strain. Furthermore, the intracellular and extracellular fluids of the strain were used to degrade tetracycline, so as to determine the location of the active substance for degradation. Finally, the toxicity of the degradation products was assessed. [Results] The strain MEH2305 was screened out and identified asEnterobacter hormaechei, which showed the best degradation performance at pH 7.0 and with tryptone as the carbon source. Strain MEH2305 showed a total tetracycline removal rate of 68% on the 7th day of culturevia abiotic degradation and bio-degradation, and the removal rates of oxytetracycline and doxycycline hydrochloride were 53% and 56%, respectively. The tetracycline removal efficiency by the intracellular and extracellular fluids of MEH2305 was 40.77% and 31.18%, respectively. Compared with tetracycline control without MEH2305, the tetracycline degradation products of MEH2305 had reduced physiological toxicity on Gram-negativeEscherichia coli K88 and Gram-positiveBacillus subtilis 168. [Conclusion] The strain MEH2305 can be used as an effective and safe tetracycline-degrading strain for the treatment of antibiotics in the environment.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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