Shear force impacts type IV pilus and flagellar dynamics during Pseudomonas aeruginosa surface adhesion

Surface-attached bacteria experience forces associated with fluid flow in nature. However, many studies on bacterial adhesion have been conducted in conditions either lacking flow or using forces not typically found in natural systems. In Chapter 2, I examine how Pseudomonas aeruginosa cells use type IV pili to interact with surfaces under host-relevant shear forces. I demonstrate that cell tilting, driven by type IV pilus retraction, predicts surface departure at low shear forces. Conversely, higher host-relevant shear forces counteract cell tilting and enhance adhesion. Thus, P. aeruginosa couples type IV pilus dynamics and cell geometry to tune adhesion to its mechanical environment. In Chapter 3, I investigate how host-relevant shear force impacts flagellar rotation during P. aeruginosa initial surface interactions. Experiments using strains having fluorescently-labeled flagella reveal that flow bends upstream-facing flagella and blocks rotation. Additionally, cells with upstream flagella exhibit fewer surface departures than cells with downstream flagella, showing that flagellar rotation drives surface departure. Therefore, these results reveal a novel role for flagellar rotation and determine how bacteria optimize surface interactions in dynamic environments. Together, these findings emphasize the need to study bacteria under mechanically relevant conditions. Shear force exerts a mechanical stress on surface attached bacterial cells, leading to prolonged surface adhesion. By integrating host-relevant conditions into bacterial research, my work has provided a clearer understanding of how P. aeruginosa optimizes surface behavior in dynamic environments.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biochemistry

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Palalay, Jessica-Jae S

Contributors dc:contributor

• Sanfilippo, Joseph E
• Huang, Raven H
• Brieher, William M
• Mera, Paola E

• Microfluidics
• shear force
• adhesion
• Pseudomonas aeruginosa
• type IV pili
• flagella

Statement dc:rights

• Copyright 2025 Jessica-Jae Palalay

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132470

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132470