Direct Quantification of Aspergillus niger Spore Adhesion in Liquid Using an Atomic Force Microscope

Area of Science:

• Microbiology
• Surface Science
• Biophysics

Background:

• Understanding microbial adhesion is crucial for various applications, including biomaterial development and infection control.
• Aspergillus niger spores are common airborne fungi with implications in health and industry.
• Quantifying adhesion at the single-cell level provides fundamental insights into spore-surface interactions.

Purpose of the Study:

• To directly quantify the adhesion forces between single Aspergillus niger spores and mica surfaces.
• To investigate the influence of electrostatic interactions (pH and ionic strength) on spore adhesion.
• To explore the role of specific spore surface features in adhesion.

Main Methods:

• Utilized Atomic Force Microscopy (AFM) with a custom
• spore probe
• technique, immobilizing single spores on AFM cantilevers.
• Measured adhesion forces by analyzing force-distance curves during spore retraction from mica surfaces.
• Conducted experiments in NaCl solutions varying pH and electrolyte concentrations.

Main Results:

• Adhesion forces were directly quantified using the AFM spore probe.
• Decreasing pH increased adhesion, indicating a contribution from reduced electrostatic repulsion.
• Adhesion magnitude did not correlate with ionic strength variations, suggesting electrostatic forces are not the sole determinant.
• Specific interactions involving spore surface appendages and protrusions play a significant role in adhesion.

Conclusions:

• The AFM spore probe is a valuable technique for studying single spore-surface interactions.
• Adhesion of Aspergillus niger spores to mica is influenced by both electrostatic factors and specific surface interactions.
• This method can aid in the fundamental study of spore adhesion and the development of materials with reduced adhesion properties.