Drivers and effects of latent phage activation in marine SAR11

病毒是海洋中最丰富的生物实体。当它们感染浮游生物时，它们可以改变食物网，引起营养循环的变化，并加强基因交换。然而，控制这些重要过程的机制在很大程度上是未知的，这限制了我们预测自然界感染结果的能力。本研究的主要目标是确定影响培养的浮游细菌中宿主-病毒相互作用的关键化学、物理和生物因素，并利用这些信息建立数学模型，预测不同海洋生态系统中的感染动态。大多数可用于详细研究的海洋病毒在感染后杀死细菌。这项新颖的研究聚焦于SAR11，一种最丰富的海洋细菌，它携带着被称为噬菌体的休眠病毒，以确定是什么导致了噬菌体激活和宿主死亡。具体而言，研究小组利用SAR11-前噬菌体对的实地调查和实验室实验来生成数据和数学模型，以预测SAR11和其他海洋微生物中病毒感染的结果。触发前噬菌体激活的条件及其对生态系统过程的相应贡献在很大程度上是假设的，主要是由于难以识别和培养具有前噬菌体的宿主细胞。越来越清楚的是，这些感染的影响和重要性没有得到充分的描述和低估。拟议的研究通过量化感染发生、鉴定噬菌体激活诱导剂和测试在宿主基因组中维持病毒DNA的影响，修订了对全球重要的SAR11中噬菌体激活的估计。前噬菌体感染的频率是通过分析长读测序技术产生的细菌宏基因组来确定的。在一系列导致应激（物理、化学和生物）的条件下进行控制生长实验，并评估基因表达的变化，以确定前噬菌体激活的驱动因素。培养中噬菌体感染的结果用于参数化数值模型中的关键相互作用，然后可以预测自然界的结果。这项研究填补了关于维持海洋中大量遗传多样性细菌和病毒种群的机制的知识空白，并有可能改变我们在不断变化的环境条件下预测宿主-病毒相互作用的理解和能力。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Viruses are the most abundant biological entities in the ocean. When they infect plankton, they can alter food webs, induce shifts in nutrient cycles, and enhance genetic exchange. However, the mechanisms that control these important processes are largely unknown, which has limited our ability to predict infection outcomes in nature. The primary goal of this study is to identify key chemical, physical, and biological factors that influence host-virus interactions in cultured bacterioplankton and to use this information to build mathematical models that predict infection dynamics in diverse marine ecosystems. Most of the marine viruses available for detailed study kill bacteria following infection. This novel study focuses on SAR11, the most abundant marine bacteria, which harbor dormant viruses called prophages, to determine what causes prophage activation and host death. Specifically, the research team uses field surveys and laboratory experiments with SAR11-prophage pairs to generate data and mathematical models to predict the outcomes of viral infections in SAR11 and other marine microbes.The conditions that trigger prophage activation and their corresponding contributions to ecosystem processes are largely hypothetical, due primarily to difficulties identifying and culturing host cells with prophages. It is becoming increasingly clear that the impact and importance of these infections are under-characterized and under-estimated. The proposed research revises estimates of prophage activation in globally-important SAR11 by quantifying infection occurrence, identifying prophage activation inducers, and testing the effects of maintaining virus DNA in the host genomes. The frequency of prophage infections is determined by analyzing bacterial metagenomes generated with long-read sequencing technology. Controlled growth experiments under a range of conditions that cause stress (physical, chemical, and biological) and evaluation of shifts in gene expression are employed to identify drivers of prophage activation. The outcomes of prophage infections in culture serve to parameterize key interactions in numerical models that can then predict outcomes in nature. This study fills critical gaps in knowledge about the mechanisms that maintain the large and genetically diverse populations of bacteria and viruses in the ocean and has the potential to change our understanding and capacity to predict host-virus interactions under changing environmental conditions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.