Structure-function relationships in expanded Type IV Secretion Systems and the conjugative F-pilus
File(s)
Author(s)
Patkowski, Jonasz
Type
Thesis
Abstract
The spread of antimicrobial resistance (AMR) is mediated by bacterial conjugation – a parasexual process that allows bacteria to horizontally exchange antibiotic resistance genes. On the molecular level, conjugation relies on protein nanomachines localised in bacterial membranes called the Type IV Secretion Systems (T4SS). They are responsible for the processing and transfer of substrate DNA across the cell envelope, and the generation of the conjugative F-pilus, which establishes direct contacts between the mating cells.
This thesis unveils the structure of TraD, a type IV coupling protein (T4CP) encoded by the F-plasmid, demonstrating its ability to bind DNA and form oligomers upon ATP hydrolysis. It documents the specific biomechanical properties of the F-pilus that enhance conjugation efficiency in severe mechanical and thermochemical environments, explaining the pervasiveness of F-plasmids in the human microbiome. This thesis reveals that such properties rely on the presence of phospholipid molecules in the F-pilus atomic structure, thereby elucidating their architectural significance for the first time, and provides the first direct visualisation of a single-stranded DNA (ssDNA) journey through the F-pilus lumen. Lastly, this thesis documents a novel T4SS that plays a role in the colonisation of human epithelial cells by adherent-invasive E. coli during Leśniowski-Crohn’s disease development, highlighting the role of T4SS in bacterial virulence.
This thesis unveils the structure of TraD, a type IV coupling protein (T4CP) encoded by the F-plasmid, demonstrating its ability to bind DNA and form oligomers upon ATP hydrolysis. It documents the specific biomechanical properties of the F-pilus that enhance conjugation efficiency in severe mechanical and thermochemical environments, explaining the pervasiveness of F-plasmids in the human microbiome. This thesis reveals that such properties rely on the presence of phospholipid molecules in the F-pilus atomic structure, thereby elucidating their architectural significance for the first time, and provides the first direct visualisation of a single-stranded DNA (ssDNA) journey through the F-pilus lumen. Lastly, this thesis documents a novel T4SS that plays a role in the colonisation of human epithelial cells by adherent-invasive E. coli during Leśniowski-Crohn’s disease development, highlighting the role of T4SS in bacterial virulence.
Version
Open Access
Date Issued
2024-04
Date Awarded
2024-07
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Dias da Costa, Tiago
Publisher Department
Life Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)