When dealing with the isolation of fungi from clinical samples, in a few cases, yeast colonies with a characteristic salmon-pink to coral-red color appear. A classic procedure of many medical mycologists is to assign such isolates to the genus Rhodotorula on the basis of this sole phenotypic attribute. Today, thanks to the improvement of molecular biology techniques (especially DNA sequencing) and molecular phylogenetics, it is well known that yeasts producing pigmented colonies (also called pigmented or red yeasts) may belong to several basidiomycetous genera other than Rhodotorula. Examples of these genera are Rhodosporidium (teleomorphic stage of many Rhodotorula species), Sporobolomyces, Sporidiobolus, Dioszegia, Cystofilobasidium, Xanthophyllomyces, and Cryptococcus. The distinctive pink-to-red coloration of their colonies is the result of the intracellular production and accumulation of carotenoid compounds. The composition of carotenoid pigments may vary qualitatively in red yeasts depending on the species. The most important carotenoids found in yeasts are torularhodin, torulene, and β-carotene.

Fil: Libkind Frati, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina