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抗生素是指用于预防或治疗人畜细菌感染产生的抗菌药物,是世界上用量最大、使用最广泛的药物之一[1]。在我国,年产抗生素原料达21万吨,使用量达18.9万吨,其中,兽用抗生素占使用量的一半以上[2]。抗生素种类众多,包括磺胺类、大环内酯类、喹诺酮类、四环素类等,其中四环素类抗生素(tetracycline antibiotics,TCs)因其价格低廉,广谱抗菌等特点,在世界各国的畜牧业中普遍使用。已有研究表明,水体[3-5]、土壤[6-7]、沉积物[8-10]等环境中均有TCs残留,且以土霉素、四环素、金霉素和强力霉素为主,残留的TCS通过食物链进入人体,从而对人体和环境产生潜在威胁[11]。
目前,土壤中抗生素的降解方法主要有理化方法和微生物降解方法两种,其中微生物降解技术因其成本低,效能高,不易产生二次污染等优势,成为众多学者的研究热点[12]。目前已筛选出的可降解四环素类抗生素降解菌属众多,但大都是降解某一种四环素类抗生素,如四环素降解菌[12-15],土霉素降解菌[16-18],金霉素降解菌[19],强力霉素降解菌[20]。翟辉[21]将筛选出的土霉素降解菌加入到污染土壤中,接入菌株的土壤中土霉素降解率比空白高30.63%;陈海宁[22]将前期筛选出的土霉素降解菌加入到污染土壤中表明,非灭菌实验组土壤中土霉素的降解率均高于空白组,土壤中菌株对土壤中土霉素的最佳降解时间为20 d。因此,研究同一菌株降解多种四环素类抗生素,修复多种四环素类抗生素污染土壤研究,减少四环素类抗生素对环境的污染和人体健康的潜在威胁,已成为研究的热点问题。
基于此,本研究从宁夏某制药厂TCS污水处理系统的活性污泥中筛选、分离出一株可同时降解土霉素、四环素、金霉素、强力霉素的高效耐药菌株TCs-2,通过形态观察、生理生化及16S rDNA分子序列分析等手段对菌株进行鉴定,研究pH、温度、降解时间对菌株TCs-2降解土霉素、四环素、金霉素、强力霉素的影响,并探究其在土壤修复过程的实际应用效果,旨在为菌株用于四环素类抗生素污染土壤环境修复提供一定的参考依据。
一株同时降解4种四环素类抗生素降解菌的筛选及降解特性
Screened and degradation characteristics of a four tetracycline antibiotics degrading bacterium
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摘要: 选取土霉素、四环素、金霉素及强力霉素作为目标污染物,采用富集驯化法从宁夏回族自治区某药厂的活性污泥中筛选出一株可同时降解这4种四环素类抗生素的降解菌TCs-2。经形态、生理生化特征及16S rDNA分析,初步鉴定为潘多拉菌属(Pandoraea sp.),进而研究该菌株的生长曲线呈S型增长,最后通过单因素试验研究了不同环境(pH、温度、降解时间)对该菌株降解特性的影响,同时考察该菌株对人工污染土壤中四环素类抗生素的降解效果。结果表明,降解的最佳pH值为6,对土霉素、四环素、金霉素及强力霉素的降解率分别为85.00%、44.58、57.63%、43.87%;最佳温度为30℃,对土霉素、四环素、金霉素及强力霉素的降解率分别为89.39%、42.78%、56.10%、32.20%;降解时间对四环素类抗生素的降解效果影响较小,11 d时土霉素、四环素、金霉素及强力霉素的降解率分别可达87.62%、42.63%、47.30%、37.96%;人工污染土壤不投放菌株和投加菌株试验结果为,在不添加菌悬液的土壤中,21 d时未灭菌土壤中土霉素、四环素、金霉素及强力霉素的降解率高于灭菌土壤,土著微生物能降解土壤中微量的四环素类抗生素;在添加菌液的土壤中,21 d时未灭菌土壤中土霉素、四环素、金霉素及强力霉素的降解率分别为70.50%、56.38%、57.55%、22.18%,灭菌土壤中土霉素、四环素、金霉素及强力霉素的降解率分别为60.38%、47.89%、55.29%、31.15%,均高于不添加菌悬液未灭菌或灭菌土壤中土霉素、四环素、金霉素及强力霉素的降解率,菌株TCs-2对土壤中土霉素、四环素、金霉素及强力霉素的4种四环素类抗生素具有较为高效的降解能力。
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关键词:
- 四环素类抗生素降解菌 /
- 降解特性 /
- 土壤修复
Abstract: Astrain, named TCs-2, capable of simultaneously oxytetracycline, tetracycline, chlortetracycline and doxycyclineand was isolated by culture enrichment method from activated sludge of pharmaceutical factory in Ningxia. Based on the morphology, physiological characteristic and 16S rDNA sequence analysis, TCs-2 was identified as Pandoraeasp. Furthermore, the growth curve of the strain showed an S-shaped growth. Finally, the influence of different environments (pH, temperature, degradation time) on the degradation characteristics of the strain was studied by single factor test, and the degradation effect of the strain on tetracycline antibiotics in artificially contaminated soil was also investigated. The results showed that the optimum degradation pH was 6, and the degradation rates of oxytetracycline, tetracycline, chlortetracycline and doxycycline were 85.00%, 44.58%, 57.63% and 43.87%, respectively. The optimum temperature was 30℃, and the degradation rates of oxytetracycline, tetracycline, chlortetracycline and doxycycline were 89.39%, 42.78%, 56.10% and 32.20%, respectively. The degradation rate of oxytetracycline, tetracycline, chlortetracycline and doxycycline were 87.62%, 42.63%, 47.30% and 37.96% after 11 days, respectively. The test results of artificially contaminated soil without and with strains were as follows: The degradation rate of oxytetracycline, tetracycline, chlortetracycline and doxycycline in the non-sterilized soil was higher than that of the sterilized soil at 21 d, and the indigenous microorganisms could degrade trace tetracycline antibiotics in the soil. When adding strain of soil, 21 d not sterilized soil degradation rate of oxytetracycline, tetracycline, chlortetracycline and doxycycline were 70.50%, 56.38%, 57.55%, 22.18%, sterilized soil degradation rate of oxytetracycline, tetracycline, chlortetracycline, and doxycycline were 60.38%, 47.89%, 55.29% and 31.15%, respectively, which were all higher than that of the soil without adding strains. Strains TCs-2 had high degradation of tetracycline, tetracycline, chlortetracycline and doxycycline in soil.-
Key words:
- TCs degrading bacteria /
- degradation characteristics /
- soil remediation
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表 1 梯度洗脱程序
Table 1. Gradient elution procedures
时间/min
Time甲醇
Methanol0.01 mol·L−1三氯乙酸
0.01mol·L−1 Trichloroacetic acid0.01 mol·L−1草酸
0.01mol·L−1 Oxalic acid乙腈
Acetonitrile0 1% 20% 75% 4% 6 6% 20% 50% 24% 12 10% 20% 30% 40% 15.5 10% 20% 30% 40% 16 1% 20% 75% 4% 25 1% 20% 75% 4% 表 2 不同菌株的降解率
Table 2. Degradation rate of different strains
降解菌
Degradation bacteria降解率/%
Degradation rate土霉素
Oxytetracycline四环素
Tetracycline金霉素
Chlortetracycline强力霉素
DoxycyclineTCs-1 91.64±0.06 41.01±0.03 30.02±0.01 9.38±0.02 TCs-2 83.19±0.04 39.96±0.01 45.91±0.04 33.43±0.01 TCs-3 68.07±0.05 20.48±0.08 50.74±0.06 34.47±0.01 TCs-4 61.22±0.04 15.10±0.01 35.83±0.04 32.00±0.02 TCs-5 82.97±0.03 30.10±0.01 20.43±0.07 4.23±0.04 TCs-6 68.37±0.11 25.06±0.03 37.93±0.10 2.45±0.02 注:降解率为平均数±标准差. Note: degradation rate is mean ± standard deviation. 表 3 菌株TCs-2的生理生化特征
Table 3. Physiological and biochemical characteristics of TCs-2
指标 Indicators 结果 Results 革兰氏染色 − 接触酶 + 甲基红 − V-P测定 − 淀粉水解 + 反硝化 − 脲酶 − 吲哚 + 注:“+”为阳性;“−”为阴性. Note: “+” is positive; “−” is negative. -
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