Bacteria beneath the West Antarctic ice sheet.

Area of Science:

• Microbiology
• Geochemistry
• Polar Science

Background:

• Subglacial environments beneath polar ice sheets are increasingly recognized as potential biospheres.
• Direct evidence for microbial life in Antarctic sub-ice sheet environments has been lacking, with only indirect indications from Lake Vostok.

Purpose of the Study:

• To investigate microbial life in sediments from beneath the West Antarctic Ice Sheet.
• To characterize the diversity and abundance of microbial communities in this subglacial environment.

Main Methods:

• Analysis of 16S rRNA gene diversity in sediment samples.
• Isolation and characterization of microbial cultures from subglacial sediments.
• Samples were collected from beneath the Kamb Ice Stream and stored at 4°C for 15 months.

Main Results:

• Abundant microbial cells (approximately 10^7 cells g^-1) were detected in the subglacial sediments.
• Low microbial diversity was observed, with only five phylotypes identified, potentially due to storage enrichment.
• Isolated microbes demonstrated cold tolerance, and their 16S rRNA gene diversity was a simplified subset of that found in other subglacial environments.

Conclusions:

• This study provides the first direct evidence of microbial ecosystems within sediments beneath the Antarctic Ice Sheet.
• The subglacial environment harbors a substantial, previously unrecognized microbial cell and organic carbon pool.
• These findings have potential implications for understanding global geochemical cycles.