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

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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.