Isolation of fungi from Lake Vostok accretion ice

Abstract

Here we report the characterization of fungi from 10 accretion ice sections (3300–5100 y old) as well as two deep glacial ice sections that are close to the bottom of the glacier (1 000 000–2 000 000 y old) from the Vostok, Antarctica, 5G ice core. Fungi were characterized by fluorescence microscopy culturing and sequence analyses of ribosomal DNA internal transcribed spacers. A total of 270 fungal colonies were cultured from the accretion ice of subglacial Lake Vostok and an additional 14 from the glacial ice immediately above the accretion ice. Mean concentrations were 0–4.42 cells mL⁻¹ ice meltwater of which 0–100% exhibited viability (as determined by fluorescence microscopy). Thirty-one unique fungal ribosomal DNA sequences (28 from accretion ice and three from glacial ice) were determined and compared to recent taxa. The results, plus tests for growth at low temperatures, indicated that Lake Vostok contains a mixture of heterotrophic psychrotolerant fungal species. This indicates that the lake is not sterile but contains a unique ecosystem.

• Antarctica
• heterotrophs
• ITS
• subglacial lake

We thank Prof Sergey Bulat and Jean-Robert Petit for useful comparisons and collaborations on some of the assays and for providing sections of the Russian allocation of Vostok accretion ice. Most of the laboratory work was performed by TD and RV. VT worked on the 3619 m ice core section. We thank Marilyn Cayer for her excellent help with fluorescence and electron microscopy. This study was supported by a grant from NSF (ANT 0536870).