Spatial structure and nutrients promote invasion of IncP-1 plasmids in bacterial populations
Spatial structure and nutrients promote invasion of IncP-1 plasmids in bacterial populations
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DOI：
10.1038/ismej.2008.53
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发表时间：
2008-10-01
期刊：
影响因子：
11
通讯作者：
Top, Eva M.
中科院分区：
文献类型：
--
作者：
Fox, Randal E.;Zhong, Xue;Top, Eva M.
尽管质粒在细菌适应中的重要性，但我们对它们的动力学了解甚少。当没有选择质粒编码的特性时，质粒是否或如何在细菌种群中持续存在并传播（侵入）尚不清楚。此外，人们对空间结构种群和混合种群之间的动态差异了解甚少。通过联合实验/理论方法，我们验证了一种假设，即自传播的IncP-1质粒可以在没有选择的情况下入侵细菌种群，当最初非常罕见时，但仅在空间结构栖息地和营养物质定期补充时。使用不同空间结构程度和营养水平的方案，在大肠杆菌中监测质粒pB10的侵袭性至少15天，携带质粒（p(+)）的细胞的初始比例低至10（-7）。为了进一步探索质粒动力学的机制，我们开发了一个空间显式数学模型。当细胞在过滤器上生长并每天转移到新鲜培养基中时，p（+）分数增加到13%，而当群体结构每天受到干扰时，p（+）分数几乎完全入侵。质粒不能在液体中侵入。当碳源水平较低或不补充时，质粒的入侵受到阻碍。数学模型的模拟结果与实验结果非常吻合，并对不同实验参数的影响进行了估计。这使我们能够分离出最可能导致观测结果的机制。综上所述，空间结构和养分有效性可能是质粒入侵的关键决定因素。
In spite of the importance of plasmids in bacterial adaptation, we have a poor understanding of their dynamics. It is not known if or how plasmids persist in and spread through (invade) a bacterial population when there is no selection for plasmid-encoded traits. Moreover, the differences in dynamics between spatially structured and mixed populations are poorly understood. Through a joint experimental/theoretical approach, we tested the hypothesis that self-transmissible IncP-1 plasmids can invade a bacterial population in the absence of selection when initially very rare, but only in spatially structured habitats and when nutrients are regularly replenished. Using protocols that differed in the degree of spatial structure and nutrient levels, the invasiveness of plasmid pB10 in Escherichia coli was monitored during at least 15 days, with an initial fraction of plasmid-bearing (p(+)) cells as low as 10(-7). To further explore the mechanisms underlying plasmid dynamics, we developed a spatially explicit mathematical model. When cells were grown on filters and transferred to fresh medium daily, the p(+) fraction increased to 13%, whereas almost complete invasion occurred when the population structure was disturbed daily. The plasmid was unable to invade in liquid. When carbon source levels were lower or not replenished, plasmid invasion was hampered. Simulations of the mathematical model closely matched the experimental results and produced estimates of the effects of alternative experimental parameters. This allowed us to isolate the likely mechanisms most responsible for the observations. In conclusion, spatial structure and nutrient availability can be key determinants in the invasiveness of plasmids.