Analysis of bacterial adhesion using a gradient force analysis method and colloid probe atomic force microscopy.

Area of Science:

• Microbiology
• Biophysics
• Materials Science

Background:

• Atomic force microscopy (AFM) is used to study bacterial adhesion by analyzing force curves.
• Defining the precise tip-bacterium distance is challenging due to bacterial surface deformation.
• Previous methods struggled to accurately quantify adhesive interactions.

Purpose of the Study:

• To develop and apply a gradient force curve analysis method for bacterial adhesion.
• To investigate the relationship between bacterial surface properties and adhesion to glass.
• To differentiate interaction regions during AFM tip-bacterium surface contact.

Main Methods:

• Colloid probe AFM was used to obtain approach and retraction force curves for three Escherichia coli strains.
• A novel gradient force curve analysis method was developed to model colloid-surface interactions.
• Sticking coefficients were measured using packed bed flow through column tests.

Main Results:

• Gradient analysis identified four interaction regions: noninteraction, noncontact (28-59 nm), contact (59-113 nm), and constant compliance.
• The noncontact phase, linked to extracellular polymers, correlated with measured sticking coefficients.
• No correlation was found between sticking coefficients and other phases or retraction curve parameters.

Conclusions:

• The length of the noncontact phase, influenced by bacterial exopolymers, is a key factor in bacterial adhesion to glass.
• Gradient force curve analysis provides valuable insights into the role of surface exopolymers in bacterial adhesion.
• This method enhances the understanding of bacterial stickiness and surface interactions.