Graduation Year

2020

Date of Submission

12-2019

Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts

Department

Biology

Reader 1

Todd Gray

Reader 2

Kyle Jay

Abstract

Bacteria use secretion systems to export proteins from inside of the bacterium into the periplasm, extracellular space, or host cell. Within the Mycobacterium genus, the type VII secretion systems (T7SS) transport products across the unusually thick and waxy mycobacterial envelope. T7SS are of particular importance because they are involved in the virulence of pathogenic mycobacteria. Mycobacteria have as many as five distinct T7SS called ESX systems. ESX-1, 3, and 5, have demonstrated roles in viability and virulence in certain pathogenic species like M. tuberculosis and M. marinum. Our research focuses on the ESX-4 apparatus, the ancestral system that gave rise to the other ESX systems. Although ESX-4 is the smallest, it shares the hallmark characteristics of ESX systems including a membrane protein complex and predicted secreted substrates containing a WXG100 motif necessary for secretion. In M. smegmatis, ESX-4 is required for Distributive Conjugal Transfer (DCT), a form of horizontal gene transfer during which a donor cell transfers segments of its genome to a recipient cell, which can lead to the transfer of traits such as antibiotic resistance. However, the mechanism of protein secretion via the ESX-4 system is still unknown. Through a mycobacterial protein fragment two-hybrid complementation assay, we will identify protein interactions within the ESX-4 system. As bacterial mRNA is polycistronic, we will initially examine interactions of proteins encoded on the same mRNA. These high priority proteins include putative ESX secreted products. Our results will demonstrate protein-protein interactions relevant to the ESX-4 system of M. smegmatis, which will allow us to further understand its mechanism of secretion and increase our knowledge of T7SS.

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