摘要
为筛选出具有高效降解土霉素能力的菌株并研究其降解特性,选取普遍使用且廉价广谱的抗生素之一——土霉素作为目标污染物,筛选了两株能降解土霉素的菌株,研究其形态、生理生化并提取其DNA,进行基因测序分析,考察其在不同的菌株混合比、接种量、初始浓度、pH、温度及外加碳源、氮源降解环境条件下的联合降解效果.初步鉴定两菌株分别为埃希菌属和芽孢杆菌属,均可以在以土霉素为唯一碳源的无机盐培养基中生长.两菌株在土霉素初始浓度为65 mg·L-1、两株菌株混合接种比例为1∶1、接种量为3%、pH为5、温度为35℃、外加碳源为麦芽糖、外加氮源为硝酸钠时的降解率最高,为最佳降解条件,其中外加碳、氮源对降解菌降解土霉素的影响最大.研究发现4种潜在的土霉素降解途径,降解过程主要有苯环裂解、脱氢、脱水、脱羰基、脱甲基、脱羟基、脱胺基和脱酰胺基反应.研究表明,试验筛选的两种降解菌能够有效降解环境中的土霉素,具有一定的研究和应用价值,可进一步用于降解和消除畜禽粪便和农田土壤残留抗生素.
Abstract
Oxytetracycline,a widely used,cheap,broad-spectrum antibiotic,was selected as the target pollutant to screen out strains of bacteria with a high ability to degrade oxytetracycline and explore their degradation characteristics.This study identified two strains capable of degrading oxytetracycline and analyzed their morphology,physiological,and biochemical characteristics and DNA sequencing of two strains.The degradation performance was investigated under different strain mix ratios,inoculation amounts,initial concentrations,pH,temperature,and additional carbon and nitrogen sources.The results indicate that the two strains were Escherichia and Bacillus sp.Both strains could grow in an inorganic salt medium with oxytetracycline as the only carbon source.The results showed that the degradation rate was the highest when the initial concentration of oxytetracycline was 65 mg·L-1,the mixed inoculation ratio was 1∶1,the inoculation amount was 3%,the pH was 5,the temperature was 35℃,the added carbon source was maltose,and the added nitrogen source was sodium nitrate.The highest degradation rate was obtained when carbon and nitrogen sources were added.Four potential degradation pathways of oxytetracycline were found.The main degradation processes were benzene ring cleavage,dehydrogenation,dehydration,decarbonylation,demethylation,dehydroxylation,deamination,and deamidation.The two bacteria were capable of degrading oxytetracycline in the environment effectively,which merits further investigation and has potential,in application,to degrade and remove oxytetracycline from animal manure and farm soil.
维普
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