Shoham Y, Demain A L
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Enzyme Microb Technol. 1990 May;12(5):330-6. doi: 10.1016/0141-0229(90)90160-r.
Recombinant plasmid pCED3 [confers beta-galactosidase production (LacZ+) and kanamycin resistance (Kmr)] in Bacillus subtilis was found to be both segregationally and structurally unstable. Since many solutions to segregational instability are already available, the problem of structural instability was specifically addressed by inclusion of kanamycin in the growth media. Culture instability was found to be highest in complex and defined media supporting high growth rates. Stabilization over the duration of the experiment (40 generations) was achieved by use of a recently developed chemically defined medium supporting a lower growth rate. Slowing down growth by decreasing temperature was much less effective. A major effect of the growth medium appears to be that of decreasing the growth rate advantage held by cells with plasmid deletions over parental cells containing the intact plasmid.
在枯草芽孢杆菌中发现重组质粒pCED3[赋予β-半乳糖苷酶产生（LacZ+）和卡那霉素抗性（Kmr）]在分离和结构上均不稳定。由于已经有许多解决分离不稳定性的方法，因此通过在生长培养基中加入卡那霉素专门解决了结构不稳定性问题。发现在支持高生长速率的复杂和限定培养基中培养不稳定性最高。通过使用最近开发的支持较低生长速率的化学限定培养基，在实验持续时间（40代）内实现了稳定。通过降低温度来减缓生长效果要差得多。生长培养基的一个主要作用似乎是降低含有质粒缺失的细胞相对于含有完整质粒的亲代细胞所具有的生长速率优势。
