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 Botan y 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 charac teristics, we were able to identify the strain GS as a yeast belonging to t he genus Cryptococcus. Some characteristics of this genus are the growth re sponse to myo-inositol, celobiose, raffinose and D-glucuronate, no-fermenta tion, the absence of mycelium and pseudomycelium, asexual reproduction, Dia zolium blue B test (DBB) and urea hydrolisis positive and the growth withou t vitamines. This strain (GS) formed cream colonies of slimy appearance wit h cells of 3x2 mu m 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 characterizatio n by whole-cell proteins and RFLP analysis of the 5.8S rRNA gene and the tw o ribosomal internal transcribed spacers (5.8S-ITS region), revealed that t his strain was different from other antarctic species of this genus. The ph ylogenetic tree deduced from the 5.8S rRNA gene sequence showed the strain G5 as a member of the genus Cryptococcus, clearly separated from other basi diomycetous yeasts. On the basis of the physiological, genotypical and phyl ogenetical data, the new isolate G5 was described as Cryptococcus victoriae , sp. nov., with the type strain G5 (= CECT 11114).