Burian J, Tu N, Kl'ucár L, Guller L, Lloyd-Jones G, Stuchlík S, Fejdi P, Siekel P, Turna J
Department of Molecular Biology, Faculty of Science, Comenius University, Bratislava, Slovakia.
Folia Microbiol (Praha). 1998;43(6):589-99. doi: 10.1007/BF02816374.
A determinant encoding resistance against potassium tellurite (Te(r)) was discovered in a clinical isolate of Escherichia coli strain KL53. The strain formed typical black colonies on solid LB medium with tellurite. The determinant was located on a large conjugative plasmid designated pTE53. Electron-dense particles were observed in cells harboring pTE53 by electron microscopy. X-Ray identification analysis identified these deposits as elemental tellurium and X-ray diffraction analysis showed patterns typical of crystalline structures. Comparison with JCPDS 4-0554 (Joint Committee on Powder Diffraction Standards) reference data confirmed that these crystals were pure tellurium crystals. In common with other characterized Te(r) determinants, accumulation studies with radioactively labeled tellurite showed that reduced uptake of tellurite did not contribute to the resistance mechanism. Tellurite accumulation rates for E. coli strain AB1157 harboring pTE53 were twice higher than for the plasmid-free host strain. In addition, no efflux mechanism was detected. The potassium tellurite resistance determinant of plasmid pTE53 was cloned using both in vitro and in vivo techniques in low-copy-number vectors pACYC184 and mini-Mu derivative pPR46. Cloning of the functional Te(r) determinant into high-copy cloning vectors pTZ19R and mini-Mu derivatives pBEf and pJT2 was not successful. During in vivo cloning experiments, clones with unusual "white colony" phenotypes were found on solid LB with tellurite. All these clones were Mucts62 lysogens. Their tellurite resistance levels were in the same order as the wild type strains. Clones with the "white" phenotype had a 3.6 times lower content of tellurium than the tellurite-reducing strain. Transformation of a "white" mutant with a recombinant pACYC184 based Te(r) plasmid did not change the phenotype. However, when one clone was cured from Mucts62 the "white" phenotype reverted to the wild-type "black" phenotype. It was suggested that the "white" phenotype was the result of an insertional inactivation of an unknown chromosomal gene by Mucts62, which reduced the tellurite uptake.
在大肠杆菌KL53临床分离株中发现了一个编码对亚碲酸钾（Te(r)）抗性的决定簇。该菌株在含亚碲酸盐的固体LB培养基上形成典型的黑色菌落。该决定簇位于一个名为pTE53的大型接合质粒上。通过电子显微镜在携带pTE53的细胞中观察到电子致密颗粒。X射线鉴定分析将这些沉积物鉴定为元素碲，X射线衍射分析显示出典型的晶体结构图案。与JCPDS 4 - 0554（粉末衍射标准联合委员会）参考数据比较证实这些晶体是纯碲晶体。与其他已表征的Te(r)决定簇一样，用放射性标记的亚碲酸盐进行的积累研究表明，亚碲酸盐摄取减少对耐药机制没有贡献。携带pTE53的大肠杆菌AB1157菌株的亚碲酸盐积累率比无质粒宿主菌株高两倍。此外，未检测到外排机制。使用体外和体内技术在低拷贝数载体pACYC184和迷你Mu衍生物pPR46中克隆了质粒pTE53的亚碲酸钾抗性决定簇。将功能性Te(r)决定簇克隆到高拷贝克隆载体pTZ19R和迷你Mu衍生物pBEf和pJT2中未成功。在体内克隆实验期间，在含亚碲酸盐的固体LB上发现了具有异常“白色菌落”表型的克隆。所有这些克隆都是Mucts62溶原菌。它们的亚碲酸盐抗性水平与野生型菌株处于同一水平。具有“白色”表型的克隆的碲含量比亚碲酸盐还原菌株低3.6倍。用基于重组pACYC184的Te(r)质粒转化“白色”突变体不会改变表型。然而，当一个克隆从Mucts62中消除时，“白色”表型恢复为野生型“黑色”表型。有人提出“白色”表型是Mucts62插入未知染色体基因导致其失活的结果，这降低了亚碲酸盐的摄取。
