عنوان

Defining the role of bacteriophage in mucosal immunity

Number

TL5px2x5b7

.Language of Text, Soundtrack etc

انگلیسی

Title Proper

Defining the role of bacteriophage in mucosal immunity

General Material Designation

[Thesis]

First Statement of Responsibility

Benler, Sean

Subsequent Statement of Responsibility

Rohwer, Forest

Date of Publication, Distribution, etc.

2018

Body granting the degree

Rohwer, Forest

Text preceding or following the note

2018

Text of Note

Since their discovery over one hundred years ago, bacteriophages (phages) play a central role in the ongoing molecular biology revolution. As such, model phages like Lambda and T4 are perhaps the most genetically well-understood biological entities. Yet, critical aspects regarding the life histories of these phages, nevertheless non-model phages, remain unaddressed. This dissertation examines the life history of T4 and non-model phages. In chapter 2, the steps involved in the morphogenesis of T4-like phages were reevaluated. During the final stages of morphogenesis, T4 packages DNA into an empty head that is subsequently joined with a tail to make a mature virion. Bioinformatic analysis of one gene involved in this head-to-tail joining process, gene 4 (gp4), identified a previously unrecognized nuclease motif. Biochemical analysis confirmed the DNA-cutting capabilities of gp4. The nuclease function of gp4 is shown to be conserved in T4-like phages. In aggregate, the data contained in chapter 2 of this dissertation suggests gp4 plays a role in the termination of genome packaging to enable head-tail joining. Chapter 3 is dedicated to the analysis of non-model phages, focusing on those that contain diversity-generating retroelements (DGRs). DGRs are genetic cassettes that introduce sequence variation into target genes. Few isolated phages possess a DGR, yet metagenomic analyses reveal their presence in uncultured viral communities. In chapter 3, a survey identified 92 DGRs that were only found in phages exhibiting a temperate lifestyle. One novel temperate phage that possesses a DGR cassette targeting a gene of unknown function was isolated from Bacteroides dorei. This phage, here named Hankyphage, exhibits broad host-range and is capable of infecting at least 13 different Bacteroides species. Sequencing reads from whole-community metagenomes and viromes were recruited to the Hankyphage genome, highlighting the global distribution of Hankyphage. The results in chapter 3 suggest that targeted hypervariation by temperate phages, such as Hankyphage, may be a ubiquitous mechanism underlying phage-bacteria interaction in the human microbiome.

Brown-Altvater, Florian

Benler, Sean

UC San Diego

Electronic name

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[Thesis]

276903

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