Cryptococcus neoformans: Budding Yeast and Dimorphic Filamentous Fungus

Cryptococcus neoformans and Cryptococcus gattii are closely related basidiomycetous fungi that commonly infect humans to predominantly cause meningoencephalitis. Both grow as budding yeasts in the environment and in the infected host yet undergo a dimorphic transition to a filamentous monokaryon or dikaryon during sexual reproduction. This chapter covers recent exciting advances in the field with special consideration of features of the virulence and life cycle relevant to studies of filamentous fungi and the emergence of microbial pathogens successfully infecting animals. The iron regulatory network and iron acquisition functions have been examined in some detail for C. neoformans. Initially, the response of the fungus to iron deprivation was examined by transcriptional profiling, and this study identified general patterns of gene expression as well as specific iron-responsive functions. The latter genes encoded iron acquisition functions and a predicted mannoprotein described as a cytokine-inducing glycoprotein (Cig1). The availability of the genome sequences and molecular techniques for C. neoformans strains provides an opportunity to define the transcriptome of the pathogen under a variety of growth conditions. An interesting recent study on extracellular proteome targeted proteins associated with extracellular vesicles. The contribution of the a allele to pathogenicity is background dependent, and virulence is a quantitative trait, in which mating-type locus (MAT) interacts with other unlinked genes to contribute to virulence.