Bacteria and archaea have been found in extreme environments, like the deepest parts of the ocean, toxic hot springs, even spacecraft bound for destinations past our atmosphere. Specifically, for years scientists (as well as sci-fi authors and filmmakers) have pondered what could be living within the frozen reaches of the Earth’s arctic caps.
Now new research from a cross-disciplinary team of geologists, chemists and biologists has revealed a diverse microbial population in a previously unsurveyed setting: a lake beneath the West Antarctic ice sheet.
Subglacial lakes were discovered in the 1960s, when it was determined that geothermal heat combined with immense pressure from the ice above can keep water from freezing. Lakes like these are especially intriguing because it’s possible they could also exist in other ice-covered places, such as Jupiter’s moon Europa. Although many have theorized that subglacial lakes could be home to microbial communities, the idea was unproven . . . until recently.
As described in Nature, the researchers used a hot water drill (which continuously circulates near-boiling water to the head of the drill) to bore through 800 meters of the West Antarctic ice sheet. Once the drill broke through to the lake below, water samples were taken and analyzed for a wide range of characteristics:
- Physical (temperature, pH, conductivity, etc.)
- Geochemical (dissolved carbon and nutrient compounds, stable isotope concentrations, etc.)
- Microbial (cell counts and composition of single-stranded ribosomal RNA molecules, to measure microbial abundance and diversity)
The results show that an active and diverse microbial community was present in the subglacial lake. Cell density was high – more than 100,000 cells per milliliter of lake water –and the samples contained almost 4,000 operational taxonomic units (OTUs, a way to define a species or species group when full classification data isn’t available).
I found the methods section of the article fascinating because it details the extensive precautions the researchers took to avoid introducing any foreign contaminants into the subglacial lake. The environment beneath the ice sheet had been isolated and untouched for thousands of years –microbial invasion from a contaminated tool could be devastating to the environment and would skew the results of the investigation. Every part of the drilling and sampling apparatus was treated with appropriate anti-microbial methods:
- Water for the hot water drill was continuously filtered, irradiated at two complementary germicidal wavelengths and pasteurized at 90°C
- Drill tubing and instrument cables were passed through a strong ultraviolet light before entering the borehole
- All sampling tools were disinfected with a 3% solution of hydrogen peroxide
- Scientists near the borehole wore single-use Tyvek protective apparel
These decontamination methods far exceed anything I’ve heard of being used in a repository lab setting, and boslter the conclusion that microbes can proliferate under hundreds of meters of ice, isolated from sun, air and the outside environment for thousands of years.
This discovery shifts our thinking about regions we consider “devoid of life”.