Phenotypic & Phylogenetic Analyses of New and Established Antarctic yeast

Abstract

Yeasts isolated from the extreme environment of Antarctica, offer a unique opportunity to exploit characteristics not found in other microorganisms. The focus of this study was sixty yeast samples originating from the Vestfold Hills area located near the Australian Davis Base, Antarctica. Functional studies of these extremophiles using a combination of classical and molecular techniques provided a correlation analysis to be achieved verifying the placement of new species against positions of existing species. Isolates were screened using one-dimensional-sodium dodecyl sulphate polyacrylamide gel electrophoresis (lD-SDS-PAGE) of whole cell proteins and yeasts grouped together according to their protein profiles. This analysis reduced the study group to 39. Phylogenetic analysis of the sequences of the Dl/D2 region and the internal transcribed spacers of the 26S ribosomal DNA determined relatedness among known yeast isolates. Sequence data revealed 2 unique species and a further 3 species that were closely related, but not identical, to established yeast species. Two isolates, shown to be indistinguishable through rDNA sequencing and protein analysis by ID-SDS-PAGE, were described as Cryptococcus watticus sp. nov. [type culture = CBS 9496T, NRRL Y-27556]. Sequence analyses of the DI/D2 region [26S] ribosomal DNA placed Cr. watticus in the Hymenomycetous yeasts in a cluster with Holtermannia corniformis and Cr. nyarrowii. This species has been allocated to the genus Cryptococcus on the basis of physiological and morphological characteristics. Sequence analyses placed five psychrophilic isolates (UNEl16c designated type strain) in the Archiascomycete clade with Leuconeurospora pulcherrima and Oosporidium margaritiferum. Preliminary sequencing results using the I8S (small ribosomal subunit) region indicated that strain UNEl16c was 99.8% similar with a black, Aureobasidium-like strain. This was highly unusual as UNEl16c was orange in colour and did not produce any black meristematic cells at any stage. There were also 29 isolates that were identified as previously established basidiomycetous yeast species (Cr. victoriae, Cr. nyarrowii, Cr. gilvescens, Cr. gastricus, Cr. sp. KCTC 17063, Leucosporidium antarcticum, Rhodotorula mucilaginosa, R. laryngis, R. minuta) and ascomycetous yeast species (Candida norvegica, C. parapsilosis, Debaryomyces hansenii). Some of these yeasts have not previously been isolated from Antarctica. The number of yeasts isolated from the Vestfold Hills thus far represented the most comprehensive biodiversity data available for Antarctic yeasts.