The contribution of electrostatic forces to the process of adherence of Candida albicans yeast cells to substrates

The contribution of electrostatic interactions to the adherence process of Candida albicans and other Candida species was investigated by mixing cationic or anionic exchange resins possessing free -COO^- or -NH₄⁺ groups, respectively, on their surface. The adherence process of yeast cells to the anionic exchange resin is a saturable event that is essentially complete by 60 min. There is no measurable interaction of yeast cells with the cationic exchange resin. All clinical isolates of C. albicans, C. pseudotropicalis, one isolate each of C. tropicalis and Torulopsis glabrata possessed electrostatic charge as defined by this method, whereas two clincal isolates of C. parapsilosis, C. krusei and one isolate of C. tropicalis did not have measurable electrostatic surface charge. The adherence process to the exchange resin with the free -NH₄⁺ group was dependent upon the pH of the suspending medium and varied from one isolate to another. Fixing yeast cells, or alternatively, endothelial cells, in such a manner as to change the surface charge of both and then measuring adherence of yeast cells to the target cells was an event that was not controlled by electrostatic interactions as they are defined herein. It appears that whatever contribution electrostatic charges make to the adherence process, that at best, it is a minor contribution.