Dissertation
UNDERSTANDING INHIBITION AND ESCAPE USING BACTERIOPHAGE ɸX174
Doctor of Philosophy (PhD), Washington State University
01/2020
Handle:
https://hdl.handle.net/2376/118442
Abstract
Superinfection exclusion is a common autoinhibitory phenomenon that prevents intraspecific secondary infection and has been observed in a wide range of viruses. Here I examine a plasmid-based inhibitory system in the bacteriophage ΦX174 known as the reduction effect that is suspected to mimic superinfection exclusion found in wild phage populations. This inhibition occurs when a portion of the ΦX174 genome containing parts of the pilot protein (gene H), the replication gene (gene A), and the intergenic region between these genes, is present within a plasmid inside the host cell. The result of this provides the host cell with almost complete protection from phage infection.
Here I investigate the minimum requirements necessary for inhibition to occur with this system. I demonstrate that it is the phage pilot protein (H) that is responsible for the observed inhibition and that protein production is necessary for inhibition to occur. I find the amount of inhibition is dependent on the size of the H protein expressed and also that inhibition occurs with the whole pilot protein, suggesting that this inhibitory phenomenon mimics superinfection exclusion seen in wild populations. I then explore the ways ΦX174 is able to evolve to overcome this inhibition through the use of flow through chemostats. Recovery from the reduction effect is possible with as little as a single point mutation. Finally, I attempt to connect the reduction effect system to superinfection exclusion in wild populations by conducting competition assays between phage species using chemostats. The results of these competition assays do not match those expected purely based on phage growth rate. The few genetic differences between ΦX174 and the other wild/mutant phages seem to play a role in allowing these phages to coexist, suggesting they may provide some benefit in a competitive environment.
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Details
- Title
- UNDERSTANDING INHIBITION AND ESCAPE USING BACTERIOPHAGE ɸX174
- Creators
- Clayton Bailes
- Contributors
- Elissa Schwartz (Advisor)Omar Cornejo (Committee Member)Mary Sanchez-Lanier (Committee Member)Holly Wichman (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Sciences, School of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 102
- Identifiers
- 99900581411801842
- Language
- English
- Resource Type
- Dissertation