Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, U.S.A.
Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, U.S.A.
Mol Plant Microbe Interact. 2020 Mar;33(3):402-411. doi: 10.1094/MPMI-10-19-0274-TA. Epub 2020 Jan 23.
Although bacterial host colonization is a dynamic process that requires population growth, studies often focus on comparing bacterial populations at a given time point. However, this may not reflect the dynamics of the colonization process. Time-course assays provide important insights into the dynamics of host colonization but are laborious and may still lack resolution for immediate processes affecting populations. An alternative way to address this issue, using widely accessible tools (such as quantitative PCR [qPCR]), is to take advantage of the relationship between bacterial chromosomal replication and cell division to determine population growth status at the sampling time. Conceptually, the ratio between the number of copies at the origin of replication and that at the terminus of replication should be correlated with the measured bacterial growth rate. This peak-to-trough ratio (PTR) to estimate instantaneous population growth status was tested with the slow-growing plant-pathogenic bacterium . We found no correlation between PTR and the measured growth rate when using genome-level data but overall sequencing depth of coverage trends matched theoretical expectations. On the other hand, the population growth status of was predicted by PTR when using qPCR data, which was improved by the pretreatment of cells with a photoreactive DNA-binding dye. Our results suggest that PTR could be used to determine growth status both in planta and in insect vectors. We expect PTR will perform better with fast-growing bacterial pathogens, potentially becoming a powerful tool for easily and quickly assessing population growth status.
虽然细菌宿主定植是一个需要种群增长的动态过程，但研究通常集中在比较给定时间点的细菌种群。然而，这可能无法反映定植过程的动态。时程分析提供了宿主定植动态的重要见解，但繁琐且可能仍然缺乏对影响种群的即时过程的分辨率。解决这个问题的另一种方法是利用广泛可用的工具（如定量 PCR [qPCR]），利用细菌染色体复制和细胞分裂之间的关系来确定采样时间的种群生长状态。从概念上讲，复制原点和复制末端的拷贝数之间的比值应该与测量的细菌生长速率相关。使用生长缓慢的植物病原细菌 测试了这种用于估计瞬时种群生长状态的峰谷比 (PTR)。当使用基因组水平的数据时，我们发现 PTR 与测量的生长速率之间没有相关性，但总体测序深度的覆盖趋势与理论预期相符。另一方面，当使用 qPCR 数据时，PTR 可以预测 的种群生长状态，用光反应性 DNA 结合染料预处理细胞可以提高预测效果。我们的结果表明，PTR 可用于确定 在植物和昆虫载体中的生长状态。我们预计 PTR 在快速生长的细菌病原体中表现更好，可能成为一种简单快速评估种群生长状态的有力工具。
