Evolution of the Host Range of the Bacteriophage φ6 Public Deposited

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  • March 21, 2019
Creator
  • Ferris, Martin Thomas
    • Affiliation: College of Arts and Sciences, Department of Biology
Abstract
  • The emergence of novel viral disease into naive host populations is a specific case of biological invasion. One critical component of viral disease emergence is the evolution of a virus' host range--the ability of a virus to utilize different hosts. In this dissertation I use the bacteriophage φ6 as a model system to investigate the evolution of virus host range. The expansion of a virus' host range is often the first step in emergence. I found that φ6 expands its host range by acquiring mutations that allow viral attachment to a novel host, that many mutations can expand host range, and that the majority of these mutations cause a decrease in the fitness of φ6 on its original host. I also examined whether the genetic similarity between the original host of φ6 and a novel host was predictive of characteristics of host range mutations that are important to emergence. I found that as host genetic similarity decreases, fewer mutations are capable of expanding φ6's host range, the fitness costs these mutations cause φ6 on its original host decrease, and the fitness of these host range mutants on a novel host decreases. Taken together, these results suggest that as host genetic similarity decreases, viruses should be less successful in colonizing and persisting on a novel host. Once a virus can grow on a novel host, viral adaptation is often necessary for persistence on this host. I adapted replicate populations of an expanded host range mutant of φ6 to a novel host until each population acquired a single adaptive mutation. I found that all of these mutations greatly increased the fitness of φ6 on this novel host, that they occur in many genes in the φ6 genome, and that most of these mutations do not reduce the fitness of φ6 on its original host. In conjunction with the data I collected on host range expansion, these results suggest that the expansion of a virus' host range will often be the limiting step in successful emergence.
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  • In Copyright
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  • Burch, Christina L.
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