Relation between tetR and tetA expression in tetracycline resistant Escherichia coli.
Relation between tetR and tetA expression in tetracycline resistant Escherichia coli.
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DOI：
10.1186/s12866-016-0649-z
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发表时间：
2016-03-12
期刊：
影响因子：
4.2
通讯作者：
Olsen JE
中科院分区：
文献类型：
--
作者：
Møller TS;Overgaard M;Nielsen SS;Bortolaia V;Sommer MO;Guardabassi L;Olsen JE
四环素是全世界家畜中使用最多的抗生素之一。耐药性在大肠杆菌中广泛传播，通常由四环素外排泵介导，如TetA。四环素外排泵的表达受到抑制因子TetR的严格控制，已被证明在低于mic的四环素浓度下具有四环素响应性。本研究的目的是研究四环素浓度增加对产生tetA的大肠杆菌生长的影响，并确定在四环素存在下，tetA和tetR在不同生长阶段的表达关系。在四环素浓度增加的条件下，构建了一株染色体上含有tetA和tetR的耐四环素大肠杆菌菌株。采用实时荧光定量PCR检测不同生长期4个时间点tetR和tetA的表达。产生tetA的大肠杆菌随着四环素浓度的增加滞后期延长，tetA和tetR的表达分别随着四环素浓度的增加而增加和减少。tetA和tetR mRNA水平随生长阶段的不同而变化，导致tetA/tetR比值从滞后期的约4逐渐下降到稳定期的约2。本研究表明，tetR和tetA的表达依赖于四环素浓度和生长阶段，有助于更好地了解大肠杆菌生长、四环素暴露和四环素抗性表达之间的关系。本文的在线版本（doi:10.1186/s12866-016-0649-z）包含补充材料，可供授权用户使用。
Tetracyclines are among the most used antibiotics in livestock worldwide. Resistance is widely disseminated in Escherichia coli, where it is generally mediated by tetracycline efflux pumps, such as TetA. Expression of tetracycline efflux pumps is tightly controlled by the repressor TetR, which has been shown to be tetracycline-responsive at sub-MIC tetracycline concentrations. The objective of this study was to investigate the effects of increasing tetracycline concentrations on the growth of TetA-producing E. coli, and to determine how expression of tetA and tetR related to each other in different growth phases in the presence of tetracycline. A tetracycline resistant E. coli strain containing tetA and tetR on the chromosome was constructed and cultured in the presence of increasing concentrations of tetracycline. Expression of tetR and tetA was measured at four time points in different growth phases by quantitative real-time PCR. The TetA-producing E. coli exhibited prolonged lag phase with increasing concentrations of tetracycline, while expression of tetA and tetR increased and decreased, respectively, with increasing tetracycline concentration. The levels of tetA and tetR mRNA varied depending on growth phase, resulting in a gradual decrease of the tetA/tetR ratio from approximately 4 in the lag phase to approximately 2 in the stationary phase. This study shows that the expression of tetR and tetA is tetracycline concentration- and growth phase-dependent, contributing to improved understanding of the relationships between E. coli growth, tetracycline exposure and expression of tetracycline resistance. The online version of this article (doi:10.1186/s12866-016-0649-z) contains supplementary material, which is available to authorized users.