Klemm P, Jensen L B, Molin S
Department of Microbiology, Technical University of Denmark, Lyngby.
Appl Environ Microbiol. 1995 Feb;61(2):481-6. doi: 10.1128/aem.61.2.481-486.1995.
Bacteria with a stochastic conditional lethal containment system have been constructed. The invertible switch promoter located upstream of the fimA gene from Escherichia coli was inserted as expression cassette in front of the lethal gef gene deleted of its own natural promoter. The resulting fusion was placed on a plasmid and transformed to E. coli. The phenotype connected with the presence of such a plasmid was to reduce the population growth rate with increasing significance as the cell growth rate was reduced. In very fast growing cells, there was no measurable effect on growth rate. When a culture of E. coli harboring the plasmid comprising the containment system is left as stationary cells in suspension without nutrients, viability drops exponentially over a period of several days, in contrast to the control cells, which maintain viability nearly unaffected during the same period of time. Similar results were obtained with a strain in which the killing cassette was inserted in the chromosome. In competition with noncontained cells during growth, the contained cells are always outcompeted. Stochastic killing obtained by the fim-gef fusion is at present relevant only as a containment approach for E. coli, but the model may be mimicked in other organisms by using species-specific stochastic expression systems.
已构建出具有随机条件致死性限制系统的细菌。将来自大肠杆菌fimA基因上游的可逆开关启动子作为表达盒插入到缺失自身天然启动子的致死性gef基因之前。将得到的融合体置于质粒上并转化到大肠杆菌中。与存在这种质粒相关的表型是，随着细胞生长速率降低，群体生长速率降低的幅度越来越大。在生长非常快的细胞中，对生长速率没有可测量的影响。当含有包含限制系统的质粒的大肠杆菌培养物作为静止细胞悬浮在无营养物的环境中时，与对照细胞相比，其活力在几天内呈指数下降，而对照细胞在同一时间段内活力几乎不受影响。将杀伤盒插入染色体的菌株也得到了类似的结果。在生长过程中与无限制的细胞竞争时，受限制的细胞总是会被淘汰。目前，由fim-gef融合体实现的随机杀伤仅作为大肠杆菌的一种限制方法，但通过使用物种特异性随机表达系统，该模型可能在其他生物体中得到模仿。
