A sensitive microbiological detection system for tetracyclines, utilizing an Escherichia coli strain containing a cloned tetA-lacZ gene fusion, is described. Expression of beta-galactosidase by the fusion plasmid pUB3610 remained subject to regulatory control by the TetR repressor protein, with the presence of tetracyclines in the growth medium leading to a 12-fold induction of beta-galactosidase synthesis. Because synthesis of beta-galactosidase was influenced to a small extent by the carbon source and the addition of cyclic AMP to the medium, cells were grown in the presence of cyclic AMP to enhance the sensitivity of the assay. All commonly marketed tetracyclines and some derivatives at concentrations as low as 0.1 ng/ml could be detected in the growth medium. A plate assay utilizing the fusion plasmid that detects 1 ng of tetracycline has also been developed.
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机译：描述了利用包含克隆的tetA-lacZ基因融合体的大肠杆菌菌株的四环素敏感微生物检测系统。融合质粒pUB3610的β-半乳糖苷酶的表达仍受TetR阻遏蛋白的调控，生长培养基中存在四环素，导致β-半乳糖苷酶合成诱导12倍。由于β-半乳糖苷酶的合成在一定程度上受到碳源和向培养基中添加环状AMP的影响，因此细胞在环状AMP的存在下生长以增强测定的灵敏度。可以在生长培养基中检测到所有常见的四环素和一些低至0.1 ng / ml浓度的衍生物。还开发了利用检测1 ng四环素的融合质粒的平板测定法。
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