Adhesion and Adhesives of Fungi and Oomycetes

Abstract

During the past decade there has been an increased recognition of the importance of adhesion of fungi to host surfaces–both plant and animal–before penetration (Mendgen et al. 1996; Epstein and Nicholson 1997; Hardham 2001; Osherov and May 2001; Tucker and Talbot 2001). Observational studies with microscopy indicate that many fungi adhere tenaciously onto inert surfaces such as polystyrene in addition to host substrata. This is perhaps not surprising since, for example, the aerial surfaces of plants are hydrophobic and relatively inert, and aquatic fungi can adhere to rocks. Microscopy of fungi that are in the process of adhering also indicates that fungal-substratum adhesion is mediated by a glue, i.e., a secreted macromolecule that extends from the fungus onto the adjacent surface and binds to it in a relatively non-specific manner. Here, we will primarily focus on fungal cell-substratum adhesion that is mediated by a glue. We will use the term ‘adhesin’ to indicate a molecule that mediates a comparatively specific attachment between a ligand on a fungus and a receptor on its host’s substratum. However, whether an adhesin is somewhat non-specifically “sticky” or has a conformational “good fit” for a particular substratum is not always clear, particularly with the literature on adhesion of animal pathogenic fungi to the extracellular matrices of mammalian cells. The cells of the human commensal and pathogen Candida albicans, for example, adhere to inert substrata such as polystyrene (Masuoka et al. 1999). Consequently, while we will focus on examples of glue-mediated adhesion of fungi to substrata, we will also mention some of the best-characterized examples of cell-cell adhesion in which at least one of the cells is a fungus, and the adhesin may have glue-like properties.