Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Plasmid. 2012 Mar;67(2):162-6. doi: 10.1016/j.plasmid.2012.01.005. Epub 2012 Jan 11.
Promiscuous, rolling-circle replication plasmid pMV158 determines tetracycline resistance to its host and can be mobilized by conjugation. Plasmid pLS1 is a deletion derivative of pMV158 that has lost its conjugative mobilization ability. Both plasmids replicate efficiently and are stably inherited in Streptococcus pneumoniae. We have analyzed the effect of pMV158 and pLS1 carriage on the bacterial growth rate. Whereas the parental plasmid does not significantly modify the cell doubling time, pLS1 slows down the growth of the bacterial host by 8-9%. The bases of the differential burden caused by pMV158 and pLS1 carriage are not yet understood. The negligible cost of the pMV158 parental natural plasmid on the host might explain the prevalence of small, multicopy, rolling-circle replication plasmids, even though they lack any selectable trait.
穿梭、滚环复制型质粒 pMV158 决定其宿主对四环素的抗性，并且可以通过接合进行转移。质粒 pLS1 是 pMV158 的缺失衍生物，已经失去了其接合转移能力。这两种质粒在肺炎链球菌中均能高效复制并稳定遗传。我们分析了 pMV158 和 pLS1 携带对细菌生长速率的影响。虽然亲本质粒不会显著改变细胞倍增时间，但 pLS1 会使细菌宿主的生长速度减慢 8-9%。pMV158 和 pLS1 携带造成的差异负担的基础尚不清楚。pMV158 亲本天然质粒对宿主的微不足道的代价可能解释了小的、多拷贝、滚环复制型质粒的流行，尽管它们缺乏任何可选择的特征。
