Bacteria in extreme environments
I’m surprised that I missed this report when it first came out, but saw it recently on some science blogs and I wanted to share it here. First reported at NASA, and published in the Proceedings of the National Academy of Sciences, researchers have presented findings describing microbial life from permanently ice-covered lakes of liquid water in Antarctica. Organisms in this environment are thought to have been isolated from the surface for at least 2800 years, based on C-14 dating of organic sediments. The environment at the bottom of the lake is lightless, extremely cold (-13 °C), and very salty. Finding of microorganisms in an extreme environment supports the possibility of discovering life in other locations in the Solar System that have liquid water, such as Jupiter’s moon Europa.
The approach used by scientists at NASA, the University of Chicago, and other institutions was relatively straightforward. It has been known for decades that there are many permanently ice covered lakes of water in Antarctica, and so they drilled a hole through the 10 meters of ice in Lake Vida, which is in the McMurdo Dry Valley of eastern Antarctica. The main concern of these studies when proposed is to avoid introducing contaminants from the surface into the pristine environment, and so the sampling apparatus is designed to prevent this from occurring.
The water in Lake Vida is oxygen-free, and is high in soluble reduced metals, ammonia, molecular hydrogen, as well as some dissolved organic compounds. The dissolved compounds presumably are leached from the underlying rock surface, and are utilized by microorganisms to generate energy. The researchers did not report culturing microorganisms that they found, but instead described direct microscopic observations following filtration of cells approximately 1 micrometer in diameter. Isolation of genomic DNA from populations of bacteria was used to make template DNA for polymerase chain reaction (PCR) amplification of the 16S ribosomal gene, in order to identify genetic tags on the bacteria and facilitate identification. One hundred fifty-four DNA sequences were obtained, describing 32 unique prokaryotic species that spanned 8 previously described bacterial classification groups. Interestingly, only bacterial DNA signatures were detected, with no eukaryotic or archaeal sequences. Many similar cold, briny environments typically exhibit very diverse archaeal populations, suggesting that the Lake Vida biosphere is truly isolated.