Biofilm cohesiveness measurement using a novel atomic force microscopy methodology

Area of Science:

• Microbiology
• Biophysics
• Materials Science

Background:

• Biofilms present both challenges (e.g., medical implants) and benefits (e.g., waste treatment).
• Quantifying biofilm cohesive strength is vital for predicting and managing biofilm development and detachment.
• Existing methods for measuring biofilm cohesion are limited.

Purpose of the Study:

• To develop and validate a novel atomic force microscopy (AFM) method for in situ measurement of biofilm cohesive energy.
• To investigate the relationship between biofilm depth and cohesive energy.
• To assess the effect of calcium on biofilm cohesion.

Main Methods:

• Developed a novel AFM technique to measure cohesive energy of biofilms in situ.
• Grew biofilms from activated sludge mixed cultures.
• Quantified biofilm volume displaced and frictional energy dissipated as a function of depth.

Main Results:

• Cohesive energy increased significantly with biofilm depth (0.10 to 2.05 nJ/µm³).
• This depth-dependent increase in cohesion was reproducible across multiple biofilm samples.
• Addition of 10 mM calcium during cultivation increased cohesive energy (0.10 to 1.98 nJ/µm³), confirming calcium's role in enhancing biofilm cohesiveness.

Conclusions:

• The novel AFM method provides a reproducible means to quantify biofilm cohesive energy in situ.
• Biofilm cohesion is depth-dependent and can be modulated by environmental factors like calcium.
• This technique is accessible with standard AFM instrumentation and applicable to diverse biofilm research.