PDF(Pubmed)
Abstract：
The developmental choice made by temperate phages, between cell death (lysis) and viral dormancy (lysogeny), is influenced by the relative abundance of viruses and hosts in the environment. The paradigm for this abundance-driven decision is phage lambda of E. coli, whose propensity to lysogenize increases with the number of viruses coinfecting the same bacterium. It is believed that lambda uses this number to infer whether phages or bacteria outnumber each other. However, this interpretation is premised on an accurate mapping between the extracellular phage-to-bacteria ratio and the intracellular multiplicity of infection (MOI). Here, we show this premise to be faulty. By simultaneously labeling phage capsids and genomes, we find that, while the number of phages landing on each cell reliably samples the population ratio, the number of phages entering the cell does not. Single-cell infections, performed in a microfluidic device and interpreted using a stochastic model, reveal that the probability and rate of phage entry decrease with the number of adsorbed phages. This decrease reflects an MOI-dependent perturbation to host physiology caused by phage attachment, as evidenced by compromised membrane integrity and loss of membrane potential. The dependence of entry dynamics on the surrounding medium results in a strong impact on the infection outcome, while the protracted entry of coinfecting phages increases the heterogeneity in infection outcome at a given MOI. Our findings in lambda, and similar results we obtained for phages T5 and P1, demonstrate the previously unappreciated role played by entry dynamics in determining the outcome of bacteriophage infection.
摘要：
温带噬菌体的发育选择，在细胞死亡（裂解）和病毒休眠（溶源性）之间，受环境中病毒和宿主相对丰度的影响。这种丰度驱动决策的范例是大肠杆菌的噬菌体λ，其溶源性倾向随着感染同一细菌的病毒数量的增加而增加。相信lambda使用这个数字来推断噬菌体或细菌的数量是否超过彼此。然而,这种解释的前提是细胞外噬菌体与细菌比率和细胞内感染复数(MOI)之间的准确作图.这里,我们证明这个前提是错误的。通过同时标记噬菌体衣壳和基因组，我们发现,虽然每个细胞上的噬菌体数量可靠地采样了种群比例，进入细胞的噬菌体数量没有。单细胞感染,在微流体设备中执行并使用随机模型进行解释，结果表明，噬菌体进入的概率和速率随吸附噬菌体数量的增加而降低。这种减少反映了由噬菌体附着引起的对宿主生理学的MOI依赖性扰动，膜完整性受损和膜电位损失证明了这一点。进入动力学对周围培养基的依赖性导致对感染结果的强烈影响，而在给定的MOI下，混合感染噬菌体的长期进入增加了感染结果的异质性。我们在λ中的发现，以及我们对噬菌体T5和P1获得的类似结果，证明了进入动力学在确定噬菌体感染结果方面所起的作用。
