The Virus Resistance Mechanism of Abortive Infection K in Lactococcus lactis

Du, Amy

The Virus Resistance Mechanism of Abortive Infection K in Lactococcus lactis

dc.contributor.advisor	Hynes, Michael Francis
dc.contributor.author	Du, Amy
dc.contributor.committeemember	Fraser, Marie Elizabeth
dc.contributor.committeemember	Harrison, Joe Jonathan
dc.contributor.committeemember	Niu, Dongyan
dc.contributor.committeemember	Fortier, Louis-Charles
dc.date	2023-11
dc.date.accessioned	2023-07-17T17:56:09Z
dc.date.available	2023-07-17T17:56:09Z
dc.date.issued	2023-07
dc.description.abstract	In nature, there is a constant battle between viruses and their hosts known as the evolutionary arms race, where they both continuously evolve to attempt to gain an advantage over the other. This evolutionary arms race has resulted in many mechanistic inventions, such as abortive infection (Abi) mechanisms in bacteria. In Abi mechanisms, viruses inject their genetic material into cells, but bacteria block phage replication by preventing one of the steps of phage maturation, typically resulting in cell death. This study looks at the Abi mechanism called AbiK, which is controlled by a protein of the same name that was discovered on a plasmid in Lactococcus lactis. A large portion of the study focuses on what happens in vivo during the AbiK mechanism. The normal wild-type infection, the abortive infection mediated by the AbiK protein, and the escape of the AbiK mechanism by a mutant phage are all studied for comparative analyses. Observations have shown that phage DNA replication is inhibited, and that transcription of the phage genes is delayed during the AbiK mechanism. The mutant phage can bypass these inhibitions, and successfully replicate its DNA and complete the phage lytic cycle. RNA-Sequencing experiments were conducted to narrow down the mechanism behind AbiK, and preliminary results indicate that AbiK depletes the nucleotide resources available in the cell, eventually resulting in cell death and inhibition of the phage replication cycle. A second part of this study focuses on the biochemistry of the AbiK protein. The AbiK protein has a polymerase activity that polymerizes an untemplated long single-stranded DNA that is covalently attached to the AbiK protein. This study identified which amino acid is used as a primer, which is tyrosine 44 on the AbiK protein. The release of protein structure prediction databases allowed for the analysis of a generated model of the AbiK protein, allowing for the elucidation of other biochemical functions the AbiK protein has. In addition to the polymerization activity, AbiK is hypothesized to bind to nucleotides or other proteins. The culmination of these studies allowed for insight on the AbiK mechanism, generating a hypothesis for future studies.
dc.identifier.citation	Du, A. (2023). The virus resistance mechanism of abortive infection K in Lactococcus lactis (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.
dc.identifier.uri	https://hdl.handle.net/1880/116749
dc.identifier.uri	https://dx.doi.org/10.11575/PRISM/41591
dc.language.iso	en
dc.publisher.faculty	Science
dc.publisher.institution	University of Calgary
dc.rights	University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subject	Bacteriophage
dc.subject	Defense Mechanism
dc.subject	Abortive Infection
dc.subject	Lactococcus lactis
dc.subject.classification	Microbiology
dc.subject.classification	Virology
dc.subject.classification	Biochemistry
dc.subject.classification	Biology--Molecular
dc.title	The Virus Resistance Mechanism of Abortive Infection K in Lactococcus lactis
dc.type	doctoral thesis
thesis.degree.discipline	Biological Sciences
thesis.degree.grantor	University of Calgary
thesis.degree.name	Doctor of Philosophy (PhD)
ucalgary.thesis.accesssetbystudent	I do not require a thesis withhold – my thesis will have open access and can be viewed and downloaded publicly as soon as possible.