PDF(Pubmed)
Abstract：
Bacterial cells often suffer a fitness cost after conjugative plasmids\' entry because these cells replicate slower than plasmid-free cells. Compensatory mutations may appear after tens of or a few hundred generations, reducing or eliminating this cost. A previous work based on a mathematical model and computer simulations has shown that plasmid-bearing cells already adapted to the plasmid may gain a fitness advantage when plasmids transfer into neighboring plasmid-free cells because these cells are still unadapted to the plasmid. These slow-growing transconjugants use fewer resources, which can benefit donor cells. However, opportunities for compensatory mutations in transconjugants increase if these cells become numerous (through replication or conjugation). Moreover, transconjugants also gain an advantage when transferring the plasmid, but the original donors may be too distant from conjugation events to gain an advantage. To understand which consequence prevails, we performed further computer simulations allowing versus banning transfer from transconjugants. The advantage to donors is higher if transconjugants do not transfer plasmids, mainly when donors are rare and when the plasmid transfer rate (from donors) is high. These results show that conjugative plasmids are efficient biological weapons even if the transconjugant cells are poor plasmid donors. After some time, conjugative plasmids gain other host-benefit genes, such as virulence and drug-resistance.
摘要：
细菌细胞在接合质粒进入后通常会遭受适应性成本，因为这些细胞的复制速度比无质粒细胞慢。代偿性突变可能在几十代或几百代后出现，减少或消除这种成本。先前基于数学模型和计算机模拟的工作表明，当质粒转移到相邻的无质粒细胞中时，已经适应质粒的携带质粒的细胞可能会获得适应性优势，因为这些细胞仍然不适应质粒。这些缓慢增长的变性人使用更少的资源，可以有益于供体细胞。然而,如果这些细胞变得众多（通过复制或结合），则转结合体中补偿性突变的机会增加。此外，转体在转移质粒时也获得了优势，但是原始捐赠者可能离共轭事件太远，无法获得优势。要了解哪种结果占上风，我们进行了进一步的计算机模拟，允许与禁止转体转体。如果转偶联体不转移质粒，对供体的优势更高，主要是当供体是罕见的，当质粒转移率（从供体）是高。这些结果表明,缀合质粒是有效的生物武器,即使跨缀合物细胞是不良质粒供体。过了一段时间,共轭质粒获得其他宿主受益基因，如毒力和耐药性。
