Collaborative Research: The Consequences of Phage-Bacteria Coevolution in Aquatic Environments

海洋病毒极其丰富多样。研究表明，这些病毒在调节微生物丰度和多样性方面很重要，因此可能影响海洋生态系统的营养循环。尽管它们具有重要的生态意义，但人们对海洋病毒的种群生物学或这些病毒如何与宿主相互作用知之甚少。该项目正在研究细菌及其病毒（噬菌体）在不同群落中的共同进化，以及噬菌体/细菌相互作用对细菌总体死亡率的影响。这项研究采用了双管齐下的方法，将把实验室的微观世界与海洋蓝藻和噬藻的自然群落联系起来。首先，研究人员利用天然分离的蓝藻细菌（聚藻球菌属）和噬藻体来研究聚藻球菌和噬藻体是否共同进化，磷酸盐可用性是否改变了这些相互作用的结果，以及这些相互作用对宿主死亡率的影响。其次，在实验室实验中产生的假设正在自然海洋群落中得到检验。在两年的时间里，人们从罗德岛州的沿海水域分离出了聚球菌和噬藻菌株。这个时间序列被用来检测共同进化是否正在发生，以及它如何影响自然环境中蓝藻和噬藻的基因型和表型多样性。该项目是第一个测试蓝藻和噬藻体是否经历共同进化，以及共同进化是否可能发生在对其种群动态重要的时间尺度上。此外，这些实验正在从种群生物学的角度检查病毒对海洋宿主种群的影响，而以前的研究只检查了噬菌体引起的死亡率的综合措施。

Marine viruses are extremely abundant and diverse. Studies suggest these viruses are important in regulating microbial abundance and diversity and thus may influence nutrient cycling in marine ecosystems. Despite their ecological importance, little is known about the population biology of marine viruses or how these viruses interact with their hosts. This project is examining the coevolution of bacteria and their viruses (phage) in diverse communities and the effect phage/bacteria interactions have on overall bacterial mortality rates. The research is employing a two-pronged approach that will bridge laboratory microcosms with natural communities of marine cyanobacteria and cyanophage. First, natural isolates of cyanobacteria (Synechococcus spp.) and cyanophages are being used to examine whether Synechococcus and cyanophage undergo coevolution, whether phosphate availability changes the outcome of these interactions, and the consequences of these interactions on host mortality. Second, the hypotheses generated in laboratory experiments are being tested in natural marine communities. Synechococcus and cyanophage strains are being isolated from Rhode Island coastal waters over the course of two years. This time series are being used to detect if coevolution is occurring and how it affects the genotypic and phenotypic diversity of cyanobacteria and cyanophages in the natural environment. This project is the first to test whether cyanobacteria and cyanophage undergo coevolution and whether coevolution is likely to occur on a time scale important to their population dynamics. Furthermore, the experiments are examining the consequences of viruses on marine host populations from a population biology perspective, whereas previous studies have examined only aggregate measures of phage-caused mortality.