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首页> 外文期刊>Journal of Theoretical Biology >Estimating the Instability Parameters of Plasmid-Bearing Cells. I. Chemostat Culture.
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Estimating the Instability Parameters of Plasmid-Bearing Cells. I. Chemostat Culture.

机译：估计质粒质粒细胞的不稳定性参数。一，化石文化。

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摘要

What determines the stability of plasmid-bearing cells in natural and laboratory conditions? In order to answer this question in a quantitative manner, we need tools allowing the estimation of parameters governing plasmid loss in different environments. In the present work, we have developed two methods for the estimation of the instability parameters of plasmid-bearing cells growing in chemostat. These instability parameters are: (i) selection coefficient (or cost of the plasmid)alpha and (ii) the probability of plasmid loss at cell division tau(0). We have found that generally selection coefficient alpha changes during elimination of plasmid-bearing cells due to changes in substrate concentration; hence, methods which assume constancy of alpha are intrinsically imprecise. Instead, one can estimate selection coefficient at the beginning and the end of cultivation when the substrate concentration is approximately constant. Applying developed techniques to two sets of experimental data, we have found that (i) the cost of the plasmid pBR322 depended on the dilution rate in chemostat and was higher at low dilutions; (ii) high levels of plasmid gene expression led to a high cost of the plasmid pPHL-7; (iii) the probability of plasmid loss was lower at high levels of plasmid gene expression and independent of the dilution rate. We have also discussed the application of our results to understanding the basic biology of bacterial plasmids.
机译：什么决定了携带质粒的细胞在自然和实验室条件下的稳定性？为了定量地回答这个问题，我们需要工具来估计在不同环境中控制质粒丢失的参数。在目前的工作中，我们已经开发了两种方法来估计在恒化器中生长的带有质粒的细胞的不稳定性参数。这些不稳定性参数是：（i）选择系数（或质粒成本）α和（ii）在细胞分裂tau（0）时质粒丢失的概率。我们发现，在去除质粒载体细胞的过程中，由于底物浓度的变化，选择系数α通常会发生变化。因此，假设alpha恒定的方法本质上是不精确的。相反，当底物浓度大致恒定时，可以在培养的开始和结束时估计选择系数。将发达的技术应用于两组实验数据，我们发现：（i）质粒pBR322的成本取决于在恒化器中的稀释率，并且在低稀释度时更高。 （ii）高水平的质粒基因表达导致质粒pPHL-7的高成本; （iii）在高水平的质粒基因表达下质粒损失的可能性较低，并且与稀释率无关。我们还讨论了我们的结果在理解细菌质粒基本生物学方面的应用。

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