锰氧化菌Pseudomonas sp. QJX-1对氧四环素的去除作用与机制

Mechanism of oxytetracycline removal by a manganese⁃oxidizing bacteria Pseudomonas sp.QJX⁃1

氧四环素(Oxytetracycline,OTC)的大量使用可能导致环境中抗性基因的生成和传播.锰氧化菌及其催化产生的生物锰氧化物(Biogenic manganese oxides,BMO)在自然界中广泛存在,但对其去除OTC的过程与机制仍不明确.因此,本研究探讨了锰氧化菌Pseudomonas sp.QJX⁃1对微量(5μg·L^(-1))OTC的去除作用与机制.结果表明,微量的OTC可以促进QJX⁃1的生长及其对Mn^(2+)的氧化.QJX⁃1及其催化生成的BMO对OTC的去除效果较好,在第168 h时对OTC的去除率达到99%.转录组结果表明,OTC会导致细菌的pstA、pstB、pstC、urtA和urtD等ABC转运蛋白编码基因表达上调,说明OTC可能是通过ABC转运蛋白泵出QJX⁃1体内进而让BMO更有效地接触OTC,从而达到OTC被吸附、氧化去除的目的.RT-qPCR结果表明,微量的OTC促进了细菌多铜氧化酶基因cumA的表达,提高了BMO的生成速率,增强了对OTC的去除效果.

The wide use of Oxytetracycline(OTC)may cause the spread of antibiotic resistance genes in the environment.Manganese⁃oxidizing bacteria and their produced biogenic manganese oxides(BMO)are ubiquitous in natural ecosystem,but whether and how they remove OTC are still unclear.Therefore,the mechanism of manganese⁃oxidizing bacteria Pseudomonas sp.QJX⁃1 removing OTC at trace concentration(5μg·L^(-1))was explored in this study.The results showed that trace amount of OTC could promote the growth of QJX⁃1 and the oxidation of Mn^(2+).QJX⁃1 and BMO performed well on the removal of OTC,and the ratio accounted for 99%at 168 h.Trace OTC could result in the up⁃regulation of the expression pstA,pstB,pstC,urtA,urtD,and other ABC transporter⁃encoding genes,indicating that OTC might be pumped out of QJX⁃1 through ABC transporter to allow effective contact of OTC with BMO and thereby the removal of OTC by adsorption and oxidation.Besides,trace amount of OTC promoted the expression of multi⁃copper oxidase gene cumA,which increased the BMO production rate and enhanced the removal of OTC.