Surface characterisation reveals substrate suitability for cyanobacterial phototaxis

Area of Science:

• Microbiology
• Biophysics
• Surface Science

Background:

• Cyanobacteria exhibit phototaxis, a light-guided motility crucial for survival.
• Current phototaxis studies often use hydrogels with variable surface properties.
• Microfluidic technologies offer potential for controlled surface environments.

Purpose of the Study:

• To identify optimal Micro-Electro-Mechanical System (MEMS)-compatible surfaces for cyanobacterial phototaxis assays.
• To characterize surface properties influencing cyanobacterial twitching motility.
• To correlate surface characteristics with motility performance.

Main Methods:

• Surface characterization using contact angle goniometry, white light interferometry, zeta-potential measurements, AFM, and XPS.
• Phototactic motility assays on various substrates.
• Analysis of cell-surface interactions using Derjaguin-Landau-Verwey-Overbeek (DLVO) and extended DLVO (XDLVO) theories.

Main Results:

• Motility increased 1.25-fold on surfaces with an 80° water contact angle compared to glass.
• Plasma-treated polydimethylsiloxane (PDMS) showed enhanced motility, similar to glass.
• Untreated PDMS exhibited negligible motility.
• Motility correlated strongly with adhesive forces and surface hydrophobicity/hydrophilicity.

Conclusions:

• Surface properties significantly impact cyanobacterial phototactic motility.
• Specific microfluidic-compatible surfaces can be engineered for reliable and repeatable phototaxis studies.
• Adhesive forces and surface energy are key determinants of twitching motility.