Direct quantification of Aspergillus niger spore adhesion in liquid using an atomic force microscope

An atomic force microscope has been used to quantify directly the adhesion between single Aspergillus niger spores and freshly cleaved mica surfaces. The measurements used "spore probes" constructed by immobilizing a single s pore at the apex of a tipless AFM cantilever. Adhesion was quantified from force-distance data for the retraction of the spore from the surface. Studi es in NaCl solutions over a range of pH and electrolyte concentration showe d that the decrease of long-range electrostatic repulsion with decreasing p H provided a contribution in increasing the overall adhesion, but the varia tion of such repulsion with ionic strength did not correlate with changes i n the magnitude of adhesion. Specific interactions between appendages and p rotusions on the spore surface must play an important role in adhesion. The AFM spore probe technique provides a useful new method for evaluating the interactions of spores and surfaces. It has the potential to become a power ful asset for both fundamental studies and the assessment of new materials with low adhesion properties. (C) 2000 Academic Press.