Fungal morphogenesis and virulence

Phenotypic variability in pathogenic fungi has long been correlated with vi rulence, but specific genetic and molecular mechanisms are only recently be ing unraveled. Fungal morphogenesis, reflecting the expression of several r egulated genes, and the capacity of the rising forms or phases to cause dis ease has been focused on at the XIVth Congress of the International Society for Human and Animal Mycology. Three experimental models of pathogenic fun gi have been discussed. In Cryptococcus neoformans, phenotypic variability or switching represents controlled and programmed changes rather than rando m mutations. Evaluated phenotypic traits were the capsular polysaccharide, cell and colony morphology and virulence. In the dimorphic Paracoccidioides brasiliensis, the serine-thiol proteinase from the yeast phase cleaves the main components of the basal membrane, thus being potentially relevant in fungal dissemination. In Candida albicans, relationships between adhesion p roteins and those of lymphocytes and neutrophils are related to fungal path ogenicity. Regulation of the directional growth of hyphae and its tropic re sponses are correlated with the invasive potential of C. albicans.