Viruses in Marine Food Webs

最近的证据表明，病毒在海洋食物网中可能非常重要，一些估计表明，它们是大多数细菌死亡的原因，并推动了营养循环的一个重要组成部分。如果这些估计是正确的，科学界将需要对我们的概念模型进行重大反思，并修改目前接受的许多现场测量的性能和解释。然而，到目前为止，证据只来自几个样本，方法和结果确实需要验证，才能被有信心地接受。该项目的目标是使用各种独立的方法从海洋样本中测量：(1)细菌生长情况下病毒感染的细菌死亡率和包括原生动物食草动物在内的其他来源的死亡率，以及(2)清除或摧毁游离病毒的速度和机制。目前还没有已知的直接方法来测量天然混合种群中病毒诱导的细菌死亡率，因此将使用两种间接方法：(A)含有成熟细胞内病毒的田间种群的电子显微镜，以及(B)天然病毒种群大小的变化和田间样本中的去除或衰减率。比率将与细菌生长、放牧损失和按大小分类的总死亡率的估算值进行比较，以试图为大的封闭样本汇编一个“源和汇”预算。病毒衰变和去除的速度和机制将在自然种群和培养病毒中进行研究。该项目包括一些实验室工作，但主要是在加利福尼亚州近岸和近海环境中进行的实地研究。使用多种方法，相互交叉验证，应该会大大增加对所达成的任何结论的信心。

Recent evidence suggest that viruses may be very important in marine food webs, with some estimates suggesting they are responsible for the majority of bacterial mortality, and driving a significant component of nutrient cycling. If these estimates are correct, the scientific community will need a major rethinking of our conceptual models and modification of the performance and interpretation of many currently-accepted field measurements. However, the evidence to date is only from a few samples, and the methods and results are in real need of verification before they can be accepted with confidence. The objectives of this project are to use a variety of independent methods to measure from marine samples: (1) mortality rates of bacteria from viral infection in the context of bacterial growth and mortality from other sources including protistan grazers, and (2) the rates and mechanisms by which free viruses are removed or destroy. There are no known direct means to measure virus-induced bacterial mortality in natural mixed population, so two indirect methods will be used: (a) electron microscopy of field populations containing mature intracellular viruses, and (b) native virus population size changes and removal or decay rates in field samples. Rates will be compared to estimates of bacterial growth, grazing losses, and size-fractionated total mortality in an attempt to assemble a "source and sink" budget for large enclosed samples. Rates and mechanisms of viral decay and removal will be studied with both natural populations and cultured viruses. This project includes some laboratory work, but primarily field studies to be performed in nearshore and offshore environments off California. The use of multiple methods, cross-verified with each other, should greatly increase the confidence in any conclusion that are reached.