School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, University Park, NG7 2RD, United Kingdom; Department of Microbiology, University of Sindh, Jamshoro, Pakistan.
Microbiol Res. 2013 Dec 14;168(10):661-6. doi: 10.1016/j.micres.2013.04.005. Epub 2013 May 10.
The presence of dual SOS boxes in the regulatory region of the most of colicin operons confines synthesis of colicin to times of stress, presumably to reduce the cost of its production. However, in presence of certain inducing agents, such as antibiotics, this tight control of colicin operon is usually lost. Although synthesis of most of colicins is known to be regulated by SOS response of host cell, different patterns of induction from distinct colicins against various inducing agents have been shown in recent years. In this study, we investigated the induction pattern of enzymatic colicin E9 (ColE9) synthesis following treatment with various concentrations (sub MICs) of the Norfloxacin (NOR) using pSBM23 construct which carries transcriptional fusion of SOS inducible promoter of pColE9 (ColE9p) and a fluorescent reporter gene (gfpmut2) into kanamycin resistant pColE9-J plasmid. Flow cytomtry analysis of the Escherichia coli cells containing pSBM23, following treatment with various concentrations showed that the SOS response mediated induction of the synthesis of ColE9 happens in a dose-dependent manner. In summary, our results suggest that the presence, even in a minute amount, of SOS response inducing agents such as fluoroquinolone antibiotic in natural habitat of colicinogenic population can promote such a costly antagonistic behaviour of microbes.
大多数 colicin 操纵子的调控区域中存在双 SOS 盒，这将 colicin 的合成限制在应激时期，推测是为了降低其生产成本。然而，在某些诱导剂（如抗生素）存在的情况下，这种对 colicin 操纵子的严格控制通常会丧失。尽管大多数 colicins 的合成被认为是由宿主细胞的 SOS 反应调控的，但近年来已经表明，不同的 colicins 针对不同的诱导剂表现出不同的诱导模式。在这项研究中，我们使用 pSBM23 构建体研究了在不同浓度（亚 MIC）的 Norfloxacin（NOR）处理下，酶 colicin E9（ColE9）合成的诱导模式，该构建体携带 pColE9（ColE9p）的 SOS 诱导启动子和荧光报告基因（gfpmut2）的转录融合到卡那霉素抗性 pColE9-J 质粒中。用 pSBM23 转化的大肠杆菌细胞的流式细胞术分析表明，SOS 反应介导的 ColE9 合成诱导以剂量依赖的方式发生。总之，我们的结果表明，即使在 colicin 产生菌的自然栖息地中存在少量的 SOS 反应诱导剂，如氟喹诺酮类抗生素，也可以促进微生物这种昂贵的拮抗行为。
