Isolation of Microbes from Lake Vostok Accretion Ice

Abstract

Bacteria from seven Lake Vostok accretion and two deep glacial Vostok ice core sections were characterized. The cell concentrations were low, but many of the cells were viable. From the hundreds of cultures, 18 unique bacterial rRNA gene phylotypes were determined. Lake Vostok may contain a complex microbial ecosystem.Subglacial Lake Vostok, the eighth largest lake on Earth (area ϭ 14,000 km 2 , volume ϭ 5,600 km 3 ) (9, 16), is covered by a 4-kilometer-thick layer of glacial ice. As the glacier traverses the lake over a period of 18,000 years, ice freezes (or accretes) to the bottom surface of the glacier, eventually forming a 200-m layer of accretion ice that has retained a linear and temporal record of the contents of the upper surface of the lake. The glacier passes over a shallow embayment, near an island (or peninsula), and then over part of the main lake basin. As the glacier passes through the embayment, initially it is grounded on the lakebed, and partly because of this, it collects mineral inclusions, making the ice silty (termed type I accretion ice) (13). Melting and freezing in this area, as well as a possible influx of material from a river system and/or from hydrothermal activity, may contribute to the characteristics of the type I ice (3, 14). The glacier is suspended over open water in portions of the embayment and over most of the main parts of the lake. The ice that forms over open water contains far fewer inclusions and lower concentrations of ions, organic carbon, and biomass (6,10,14). This ice is very clear ice and has been termed type II accretion ice (13). The top section (from 3,538 to 3,595 m), which accreted within and near the embayment, primarily consists of type I ice, although there are some regions of type II ice (2). Bacteria from this ice, including potentially psychrophilic and psychrotolerant species as well as the molecular signature of a thermophilic bacterium, have been reported (1,3,4,5,7,10). Within the lake, temperatures average Ϫ2°C, pressures approach 400 atmospheres, high oxygen levels exist, there are low nutrient levels, and it is completely dark.We isolated and characterized microbes from Lake Vostok type I and II accretion ice from the embayment and the main basin as well as from glacial ice immediately above the accretion ice layers. Sequence results from the rRNA small subunit genes and internal transcribed spacers indicate that at least 18 species are represented in the accretion ice. All are psychrotolerant in that they grew at 4°C, although optimal growth was often at higher temperatures.Descriptions and cell concentrations. Nine Vostok 5G ice core sections were assayed. Five sections represented ice that accreted over the shallow embayment (depths of 3,540, 3,563, 3,582, and 3,584 m, all type I ice, and 3,591 m, type II ice) (2) approximately 3,800 to 5,100 years ago (2,6,13,14), two accreted 3,400 to 3,500 years ago over the main lake basin (3,606 m, type I ice, and 3,610 m, type II ice), and two were glacial ice cores near the bottom of the glacier (3,5...

Preliminary Analysis of Life within a Former Subglacial Lake Sediment in Antarctica

“…Phylogenetic analysis of rRNA gene sequences in accretion ice formed over a deep portion of the lake revealed phylotypes that classified within the beta-, gamma-, and delta-Proteobacteria. D'Elia et al [20,21], then isolated microbes from the accretion ice from the Firmicutes, Actinobacteria and alpha-Proteobacteria; these included Nitrobacter, Caulobacter, Cryobacterium, Arthrobacter, Nocardia, Kokuria, Micrococcus, Bacillus, Frankia, Terrebacter, Carnobacterium and Paenibacillus spp.…”

Genetic Engineering of Caulobacter crescentus for Removal of Cadmium from Water

“…is a candidate for such a remediatory approach. The distribution of Caulobacter is ubiquitous, including freshwater [14], seawater [15], ground water [16], wastewater [17], drinking water [18][19][20], soil [21], deep-sea sediment [22], a gold mine [23], and even ancient ice dated back thousands of years [24]. Cells of Caulobacter are harmless to animals, humans, and the environment and are well known for their ability to survive in nutrient-poor habitats.…”

Microbial Analyses of Ancient Ice Core Sections from Greenland and Antarctica

“…Organisms belonging to these genera are tolerant to low temperatures and have been isolated from glacial and accretion ice samples from Lake Vostok [4]. Castello et al .…”