Cryptococcus

Cryptococcus is a genus of fungi in the family Cryptococcaceae that includes both yeasts and filamentous species. The filamentous, sexual forms or teleomorphs were formerly classified in the genus Filobasidiella, while Cryptococcus was reserved for the yeasts. Most yeast species formerly referred to Cryptococcus have now been placed in different genera. The name Cryptococcus comes from the Greek for "hidden sphere" (literally "hidden berry"). Some Cryptococcus species cause a disease called cryptococcosis. The genus was described by French mycologist Jean Paul Vuillemin in 1901, when he failed to find ascospores characteristic of the genus Saccharomyces in the yeast previously known as Saccharomyces neoformans. Over 300 additional names were subsequently added to the genus, almost all of which were later removed following molecular research based on cladistic analysis of DNA sequences. As a result, some ten species are currently recognized in Cryptococcus. The teleomorph was first described in 1975 by K.J. Kwon-Chung, who obtained cultures of the type species, Filobasidiella neoformans, by crossing strains of the yeast Cryptococcus neoformans. She was able to observe basidia similar to those of the genus Filobasidium, hence the name Filobasidiella for the new genus. Following changes to the International Code of Nomenclature for algae, fungi, and plants, the practice of giving different names to teleomorph and anamorph forms of the same fungus was discontinued, meaning that Filobasidiella became a synonym of the earlier name Cryptococcus. The cells of species that produce yeasts are covered in a thin layer of glycoprotein capsular material that has a gelatin-like consistency, and that among other functions, serves to help extract nutrients from the soil. The C. neoformans capsule consists of several polysaccharides, of which the major one is the immunomodulatory polysaccharide called glucuronoxylomannan (GXM). GXM is made up of the monosaccharides glucuronic acid, xylose and mannose and can also contain O-acetyl groups.