Graduate School of Agricultural Science, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan.
Graduate School of Agricultural Science, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan.
Food Microbiol. 2016 Dec;60:49-53. doi: 10.1016/j.fm.2016.05.019. Epub 2016 Jun 22.
We investigated a bacterial sample preparation procedure for single-cell studies. In the present study, we examined whether single bacterial cells obtained via 10-fold dilution followed a theoretical Poisson distribution. Four serotypes of Salmonella enterica, three serotypes of enterohaemorrhagic Escherichia coli and one serotype of Listeria monocytogenes were used as sample bacteria. An inoculum of each serotype was prepared via a 10-fold dilution series to obtain bacterial cell counts with mean values of one or two. To determine whether the experimentally obtained bacterial cell counts follow a theoretical Poisson distribution, a likelihood ratio test between the experimentally obtained cell counts and Poisson distribution which parameter estimated by maximum likelihood estimation (MLE) was conducted. The bacterial cell counts of each serotype sufficiently followed a Poisson distribution. Furthermore, to examine the validity of the parameters of Poisson distribution from experimentally obtained bacterial cell counts, we compared these with the parameters of a Poisson distribution that were estimated using random number generation via computer simulation. The Poisson distribution parameters experimentally obtained from bacterial cell counts were within the range of the parameters estimated using a computer simulation. These results demonstrate that the bacterial cell counts of each serotype obtained via 10-fold dilution followed a Poisson distribution. The fact that the frequency of bacterial cell counts follows a Poisson distribution at low number would be applied to some single-cell studies with a few bacterial cells. In particular, the procedure presented in this study enables us to develop an inactivation model at the single-cell level that can estimate the variability of survival bacterial numbers during the bacterial death process.
我们研究了一种用于单细胞研究的细菌样品制备程序。在本研究中，我们检查了通过 10 倍稀释获得的单个细菌细胞是否遵循理论泊松分布。使用了 4 种血清型沙门氏菌、3 种血清型肠出血性大肠杆菌和 1 种单核细胞增生李斯特菌作为样品细菌。通过 10 倍稀释系列制备每种血清型的接种物，以获得平均值为 1 或 2 的细菌细胞计数。为了确定实验获得的细菌细胞计数是否遵循理论泊松分布，通过最大似然估计（MLE）估计的泊松分布参数与实验获得的细胞计数之间进行似然比检验。每个血清型的细菌细胞计数都充分遵循泊松分布。此外，为了检查从实验获得的细菌细胞计数中泊松分布参数的有效性，我们将这些参数与通过计算机模拟随机数生成估计的泊松分布参数进行了比较。从细菌细胞计数中获得的泊松分布参数在使用计算机模拟估计的参数范围内。这些结果表明，通过 10 倍稀释获得的每个血清型的细菌细胞计数遵循泊松分布。在低数量下细菌细胞计数的频率遵循泊松分布的事实将适用于一些具有少数细菌细胞的单细胞研究。特别是，本研究中提出的程序使我们能够开发一种能够在单细胞水平上估计细菌死亡过程中存活细菌数量变化的失活动力学模型。
