Dynamic swimming pattern of Pseudomonas aeruginosa near a vertical wall during initial attachment stages of biofilm formation

Nicole Zi-Jia Khong,Zhao-Xun Liang,Cheng-Gee Koh,Hoi-Yeung Li,Soak-Kuan Lai,Keng-Hwee Chiam,Yukai Zeng

doi:10.1038/s41598-021-81621-w

Abstract

Studying the swimming behaviour of bacteria in 3 dimensions (3D) allows us to understand critical biological processes, such as biofilm formation. It is still unclear how near wall swimming behaviour may regulate the initial attachment and biofilm formation. It is challenging to address this as visualizing the movement of bacteria with reasonable spatial and temporal resolution in a high-throughput manner is technically difficult. Here, we compared the near wall (vertical) swimming behaviour of P. aeruginosa (PAO1) and its mutants ΔdipA (reduced in swarming motility and increased in biofilm formation) and ΔfimX (deficient in twitching motility and reduced in biofilm formation) using our new imaging technique based on light sheet microscopy. We found that P. aeruginosa (PAO1) increases its speed and changes its swimming angle drastically when it gets closer to a wall. In contrast, ΔdipA mutant moves toward the wall with steady speed without changing of swimming angle. The near wall behavior of ΔdipA allows it to be more effective to interact with the wall or wall-attached cells, thus leading to more adhesion events and a larger biofilm volume during initial attachment when compared with PAO1. Furthermore, we found that ΔfimX has a similar near wall swimming behavior as PAO1. However, it has a higher dispersal frequency and smaller biofilm formation when compared with PAO1 which can be explained by its poor twitching motility. Together, we propose that near wall swimming behavior of P. aeruginosa plays an important role in the regulation of initial attachment and biofilm formation.

Highlights

Studying the swimming behaviour of bacteria in 3 dimensions (3D) allows us to understand critical biological processes, such as biofilm formation
Mutant PAO1 lacking in the c-diGMP binding protein, FimX, required for T4P assembly biofilm formation is less capable of microcolony and biofilm formation due to deficiency in twitching m otility[6]
In particular, is a preferred method to perform 3D tracking of bacteria because it is able to capture a large depth of field and providing high throughput data

Summary

Introduction

Studying the swimming behaviour of bacteria in 3 dimensions (3D) allows us to understand critical biological processes, such as biofilm formation. In particular, is a preferred method to perform 3D tracking of bacteria because it is able to capture a large depth of field and providing high throughput data It is often limited by the lack of contrast of the samples (especially when using unlabeled cells) and secondary scattering of the bacteria, which produce poor holograms due to overlapping signals when there are too many bacteria cells[16]. These make resolving and tracking of individual cell difficult and more errors are generated when the concentration of the sample is high These techniques aim to image 3D motility of bacteria, they are not able to analyze biofilm formation on vertical surfaces

Methods

Findings

Conclusion