Bacteria beneath the West Antarctic Ice Sheet

Abstract

Summary Subglacial environments, particularly those that lie beneath polar ice sheets, are beginning to be recognized as an important part of Earth's biosphere. However, except for indirect indications of microbial assemblages in subglacial Lake Vostok, Antarctica, no sub‐ice sheet environments have been shown to support microbial ecosystems. Here we report 16S rRNA gene and isolate diversity in sediments collected from beneath the Kamb Ice Stream, West Antarctic Ice Sheet and stored for 15 months at 4°C. This is the first report of microbes in samples from the sediment environment beneath the Antarctic Ice Sheet. The cells were abundant (∼107 cells g−1) but displayed low diversity (only five phylotypes), likely as a result of enrichment during storage. Isolates were cold tolerant and the 16S rRNA gene diversity was a simplified version of that found in subglacial alpine and Arctic sediments and water. Although in situ cell abundance and the extent of wet sediments beneath the Antarctic ice sheet can only be roughly extrapolated on the basis of this sample, it is clear that the subglacial ecosystem contains a significant and previously unrecognized pool of microbial cells and associated organic carbon that could potentially have significant implications for global geochemical processes.

Subglacial Lake Whillans microbial biogeochemistry: a synthesis of current knowledge

“…The analysis of nucleic acids from SLW samples revealed three betaproteobacterial OTUs that were closely related to sequences retrieved from sediments below the KIS [18]. The closest cultured relatives to these environmental sequences included Polarmonas glacialis (5% of OTUs in SLW water and 1.8% in sediments), an aerobic heterotroph, which was also the second most abundant OTU in SLW waters [7].…”

“…Samples of this material contained microbial cells and offered the first evidence for deep subsurface life in Antarctica [6,16,17]. A sediment core collected from under the Kamb Ice Stream (KIS), West Antarctica, which is due north of Whillans Ice Stream (WIS), was also shown to contain viable microbial cells [18]. These authors concluded that the KIS sample was most likely enriched in cell numbers relative to expected in situ abundances due to prolonged storage at 4 • C. However, the organisms identified using nucleic acid sequencing and cultivation were unlikely to have resulted from contamination given the low porosity and hydraulic conductivity of the sediments [19].…”

Diversity of cultured bacteria from the perennial ice block of Scarisoara Ice Cave, Romania

“…In spite of the in depth investigation of the structural and functional microbial diversity in frozen environments (Price, 2007;Priscu et al, 2007;Margesin & Miteva, 2011;Gunde-Cimerman et al, 2012) such as polar ice sheets and glaciers (Miteva et al, 2004, Lanoil et al, 2009Rehakova et al, 2010;Anesio & Laybourn-Parry, 2012), permafrost (Rivkina et al, 2004), mountain glacier forefields (Lapanje et al, 2012;Zumsteg et al, 2012), frozen lakes (Felip et al, 1995), sea ice (Deming, 2002), Arctic (Varin et al, 2010;Adams et al, 2014) and Antarctic permanent lake ice (Priscu et al, 1998;Dieser et al, 2010, Murray et al, 2012, very little is known about microbial communities present in cave-hosted perennial ice accumulations. Such habitats are found in caves from mid-latitude, mid-altitude mountains, where the combination of cave morphology and local climatic conditions allow for the year-round preservation of ice and associated azonal glacial climatic conditions (Perşoiu & Onac, 2012).…”

Microbial communities in the subglacial waters of the Vatnajökull ice cap, Iceland

“…Investigations have described microorganisms in the seafloor (Sogin et al, 2006;Mason et al, 2010), in continental crust (Davidson et al, 2011) and beneath ice sheets (Lanoil et al, 2009). A deep microbial biosphere may be a vast reservoir of diversity (Whitman et al, 1998), a refuge for life (Sleep and Zahnle, 1998) and the setting of the origin of life itself (Martin et al, 2008).…”