Abstract
Bacterial biofilms exhibit up to 1000 times greater resistance to antibiotic or host immune clearance than planktonic cells. Pseudomonas aeruginosa produces retractable type IV pili (T4P) that facilitate twitching motility on surfaces. The deployment of pili is one of the first responses of bacteria to surface interactions and because of their ability to contribute to cell surface adhesion and biofilm formation, this has relevance to medical device-associated infections. While polymer chemistry is known to influence biofilm development, its impact on twitching motility is not understood. Here, we combine a polymer microarray format with time-lapse automated microscopy to simultaneously assess P. aeruginosa twitching motility on 30 different methacrylate/acrylate polymers over 60 min post inoculation using a high-throughput system. During this critical initial period where the decision to form a biofilm is thought to occur, similar numbers of bacterial cells accumulate on each polymer. Twitching motility is observed on all polymers irrespective of their chemistry and physical surface properties, in contrast to the differential biofilm formation noted after 24 h of incubation. However, on the microarray polymers, P. aeruginosa cells twitch at significantly different speeds, ranging from 5 to ∼13 nm/s, associated with crawling or walking and are distinguishable from the different cell surface tilt angles observed. Chemometric analysis using partial least-squares (PLS) regression identifies correlations between surface chemistry, as measured by time-of-flight secondary ion mass spectrometry (ToF-SIMS), and both biofilm formation and single-cell twitching speed. The relationships between surface chemistry and these two responses are different for each process. There is no correlation between polymer surface stiffness and roughness as determined by atomic force measurement (AFM), or water contact angle (WCA), and twitching speed or biofilm formation. This reinforces the dominant and distinct contributions of material surface chemistry to twitching speed and biofilm formation.
Highlights
When bacterial cells colonize surfaces as biofilms, structured communities of sessile cells are enmeshed within a selfgenerated extracellular matrix that provides protection from antibiotics and host immune system clearance in humans and animals
The flagella enable single bacterial cells to reach a surface by swimming through liquid environments, whereas type IV pili (T4P) are required for twitching motility employed by single cells to crawl or walk on surfaces.[4]
Bacterial surface interactions generally are complex, and our results suggest that P. aeruginosa twitching and biofilm formation cannot be explained by material hydrophobicity and surface compliance alone, an observation consistent with the literature.[27]
Summary
When bacterial cells colonize surfaces as biofilms, structured communities of sessile cells are enmeshed within a selfgenerated extracellular matrix that provides protection from antibiotics and host immune system clearance in humans and animals. P. aeruginosa cells display distinctive biological features as early as 20 min after inoculation onto a surface.[9−11] an incubation time of ∼30 min without shear stress has been shown to be necessary before significant bacterial adherence to surfaces is observed Prior to this time point, cells adhere to different surfaces with the same low adhesive force and do not proceed to later-stage biofilm formation. Partial least-squares (PLS) regression models describing the relationship between polymer surface chemistry and microbial responses allowed the identification of chemical moieties associated separately with twitching and later-stage biofilm development. Bacterial biofilm formation on each polymer spot was quantified by subtracting the background fluorescence of the control microarray coverslips from that exposed to bacteria.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
