左氧氟沙星对土壤中汞形态微生物转化的影响

Effect of levofloxacin on microbiological transformaiton of mercury speciation in soil

为阐明左氧氟沙星(Levofloxacin)对土壤中汞形态转化的影响效应,探究了左氧氟沙星对2种能够影响汞形态转化的细菌—枯草芽孢杆菌(Bacillus subtilis subsp.spizizenii)和洋葱假单胞菌(Pseudomonas cepacian)的抑菌效果;并通过室内土培试验阐明了添加左氧氟沙星对土壤汞赋存形态的作用机制.结果表明,左氧氟沙星对2种细菌都有较好的抑菌效果,在添加0.1 mg·mL^(-1)左氧氟沙星时,枯草芽孢杆菌和洋葱假单胞菌的菌群数量都有显著降低.土壤培养实验中,接种枯草芽孢杆菌处理土壤中的Hg含量显著高于对照组(p<0.05),而洋葱假单胞菌则导致土壤中Hg~0生成量明显升高(p<0.05).左氧氟沙星的添加减弱了土壤细菌对Hg和Hg~0的转化作用;这主要归因于左氧氟沙星可以有效抑制土壤中菌群的数量及过氧化氢酶和汞还原酶的活性,从而导致2种菌对Hg的氧化和还原能力下降,降低了土壤中Hg和Hg~0的含量.本研究对探究汞与抗生素复合污染土壤中汞的形态变化及其环境归趋具有一定的借鉴意义.

In order to illustrate the influence of levofloxacin on the mercury transformation in soil,this study investigated the effects of levofloxacin on Bacillus subtilis subsp.spizizenii and Pseudomonas cepacian,which are two bacteria with a substantial capacity to alter the mercury(Hg)speciation. In addition,an indoor soil incubation trial was carried out,in an attempt to reveal the mechanism concerning the roles of levofloxacin in the variation of Hg existing forms in soil. The results show that levofloxacin exhibited an remarkable inhibitory effect to both B. subtilis and P. cepacian. At the presence of 0.1 mg·mL^(-1)levofloxacin,the colony numbers of B. subtilis and P. cepacia were significantly reduced when compared to the control. In the soil incubation experiment,it was observed that the concentration of Hgor Hg~0 in the soil with the addition of B. subtilis or P. cepacian was significantly higher than those in the control(p<0.05);however,the stimulating effect of production of Hgand Hg~0 in the soil decreased in the presence of levofloxacin. This is mainly due to the fact that levofloxacin can effectively inhibit these two bacteria in soil as well as the activities of catalase and mercury reductase,lowering Hg oxidation and reduction ability of the two bacteria. Thus,the concentration of Hgor Hg~0 in soil was decreased accordingly. The outcomes of this study may fill the information gap concerning the Hg speciation variation and environmental fate in co-contaminated soil by both Hg and antibiotics.