The Role of Virus-Host Interactions in the Evolutionary Dynamics of Bacteriophage Populations

Bacteriophage (phage) are viruses which infect and replicate within bacteria cells. Phages replicate by finding a host bacteria cell, adsorbing to it, injecting their DNA, hijacking the host machinery to produce more phage, and finally lysing the cell to release the new phage. The evolutionary dynamics of phage populations are therefore strongly tied to their interactions with the host bacteria. In a spatial context, I was able to show that unavoidable physical interactions between the virus and host hinder viral dispersal, leading to a phage population in which stochastic fluctuations are much weaker. This allows beneficial mutations to establish more easily and deleterious ones to be purged, making the phage population more adaptable to changes in the environment. To facilitate better comparisons between theory and experiment in spatial contexts, I also developed a variety of new experimental techniques. These were aimed at addressing shortcomings of existing techniques, which are almost exclusively based on population averages and are carried out in well-mixed liquid cultures, making their applicability to spatial settings challenging. Finally, phages are also able to interact with each other via their host, by encoding superinfection-exclusion mechanisms which, after initial infection, prevent subsequent phage from successfully infecting that host. Using stochastic simulations, I show that in the long term such mechanisms limit the adaptive potential of the phage, by limiting the genetic diversity in the population and reducing the efficiency of selection. In the short term however, having such a mechanism provides a very large advantage over other phage in the population which lack such a mechanism, possibly explaining the ubiquity of such mechanisms in nature.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2022

Author dc:creator

• Hunter, Michael

Advisor dc:contributor.advisor

• Fusco, Diana

• bacteriophage
• virus
• evolution

Licence

• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.91071

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/343645