DISSERTATION RESEARCH: Evolution of Generalism and Specialism in the RNA phage Phi6

长期以来，生物学家一直很困惑，为什么大多数生物只专注于少数几种资源，而不是通过广泛利用自然界提供的各种资源来进行推广。通用性似乎是一个更诱人的策略，因为它允许更大的生态位空间和生物在广泛的栖息地中茁壮成长的能力。然而，专家似乎在自然界占主导地位，也许是因为他们在利用较少的资源方面效率更高。通用性的成本（及其潜在机制）已被证明难以研究。这项研究将使用RNA病毒phi-6的突变体，这些突变体显示出感染新宿主细菌（即，通才型病毒）的扩展能力，以检验通才型病毒的假设代价。突变体将在单一的新宿主上进化数百代，以测试对新宿主的适应是否需要特化（缩小病毒生态位）。此外，将对进化病毒的基因组进行测序，以测试两种相互竞争的理论，即专业化机制如何在分子水平上进化。这项研究是强有力的，因为它使用一种无害的细菌病毒来研究有关病毒转移到宿主上的一般问题。病毒phi-6是研究分节RNA病毒（如汉坦病毒和流感病毒）进化的一个特别有用的模型。因此，研究结果应进一步了解涉及高等生物致病性RNA病毒的宿主转移。

Biologists have long puzzled why most organisms specialize on few resources, rather than generalize by broadly exploiting the wide variety of resources that nature offers. Generalism seems a more tempting strategy, because it allows a larger niche space and the ability for organisms to thrive across a vast range of habitats. However, specialists appear to predominate in nature, perhaps due to their greater efficiency at exploiting a lesser number of resources. The costs of generalism (and their underlying mechanisms) have proven difficult to study. This research will use mutants of the RNA virus phi-6 that show an expanded ability to infect new host bacteria (i.e., generalist viruses), to examine hypothesized costs of generalism. The mutants will be evolved for hundreds of generations on a single novel host in order to test whether adaptation to the new host necessitates specialization (narrowing of the virus niche). Also, genomes of the evolved viruses will be sequenced to test two competing theories on how mechanisms for specialization evolve at the molecular level. This study is powerful because it uses a harmless virus of bacteria to study general questions regarding host shifts by viruses onto hosts. Virus phi-6 is an especially informative model for studying evolution of segmented RNA viruses, such as Hantavirus and Influenza which infect humans. Thus, results of the study should further the understanding of host-shifts involving pathogenic RNA viruses of higher organisms.