Investigation of flagellotropic phage interactions with their motile host bacteria

Bacteriophages cohabit with their bacterial hosts and shape microbial communities. To initiate infection, phages use bacterial components as receptors to recognize and attach to hosts. Flagellotropic phages utilize bacterial flagella as receptors. Studies focused on uncovering mechanistic details of flagellotropic phage infection are lacking. As the number of phage-based applications grows, it is important to understand these details to predict the potential outcomes of phage therapy. To this end, we studied two flagellotropic phages: Agrobacterium phage 7-7-1 and bacteriophage χ. Phage 7-7-1 infects Agrobacterium spp., while bacteriophage χ infects Salmonella and Escherichia coli. Chapter 1 consists of a literature review. Chapter 2 addresses factors underlying phage-bacteria coexistence. We document the emergence of a sector-shaped lysis pattern following co-inoculation of phage χ and one of its Salmonella hosts on swim plates. We propose that this pattern serves as a reporter for balanced phage-bacteria coexistence. Using a combined experimental and mathematical modelling approach, we discovered that variations to intrinsic factors (i.e., bacterial motility, phage adsorption) skews the pattern towards either bacterial or phage predominance. Thus, this computational model may be used to predict phage therapy application outcomes. Chapter 3 details the identification of cell surface receptors essential for phage 7-7-1 infection using a transposon mutagenesis approach. We identified three Agrobacterium sp. H13-3 genes involved in phage 7-7-1 infection. Using mass spectrometry and other analyses, we determined that the LPS profiles of strains lacking these genes varied compared to the wild type. Thus, LPS is a secondary cell surface receptor for phage 7-7-1. Chapter 4 focuses on the discovery of phage encoded receptor binding proteins (RBPs) in Agrobacterium phage 7-7-1. Using an RBP screen, we discovered three candidate RBPs. We learned that our top candidate, Gp4, inhibits the growth of Agrobacterium sp. H13-3 cells in a motility and glycan dependent manner. Because of its bacteriostatic activities, this protein is a promising candidate for therapeutic use. Overall, the described works contribute to a deepened understanding of flagellotropic phage infection and the factors influencing their coexistence with motile bacteria. These works will contribute towards the development of phage therapies using whole phage or their components.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Biological Sciences

Department dc:contributor.department

Biological Sciences

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2021

Author dc:creator

• Gonzalez, Floricel

Chair dc:contributor.committeechair

• Scharf, Birgit E.

Committee members dc:contributor.committeemember

• Caswell, Clayton C.
• Yang, Zhaomin
• Duggal, Nisha K.

• phage
• receptors
• Agrobacterium
• Salmonella
• flagellotropic

Statement dc:rights

• Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc-sa/4.0/

Dc Identifier Other

vt_gsexam:31541

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/103940