Polyphasic taxonomy of a novel yeast isolated from antarctic environment; description of Cryptococcus victoriae sp. nov.

In 1992 some samples of mosses, lichens and soils were collected from Botany Bay, Southern Victoria Land (77 degrees 01' S 162 degrees 32' E) and, as a result of a routine screening programme some yeasts were isolated. One of them, designated as strain G5, showed marked differences when compared to other antarctic yeasts. According to morphological and physiological characteristics, we were able to identify the strain G5 as a yeast belonging to the genus Cryptococcus. Some characteristics of this genus are the growth response to myo-inositol, celobiose, raffinose and D-glucuronate, no-fermentation, the absence of mycelium and pseudomycelium, asexual reproduction, Diazolium blue B test (DBB) and urea hydrolisis positive and the growth without vitamines. This strain (G5) formed cream colonies of slimy appearance with cells of 3 x 2 microns in size, that grew between 4 degrees C and 20 degrees C. The G + C content of strain G5 was 50.3 mol%. The molecular characterization by whole-cell proteins and RFLP analysis of the 5.8S rRNA gene and the two ribosomal internal transcribed spacers (5.85-ITS region), revealed that this strain was different from other antarctic species of this genus. The phylogenetic tree deduced from the 5.8S rRNA gene sequence showed the strain G5 as a member of the genus Cryptococcus, clearly separated from other basidiomycetous yeasts. On the basis of the physiological, genotypical and phylogenetical data, the new isolate G5 was described as Cryptococcus victoriae, sp. nov., with the type strain G5 (= CECT 11114).