An international team of scientists reporting in the Proceedings of the National Academy of Sciences has for the first time been able to get a complete picture of the Antarctica’s Deep Lake microbial community.
Deep Lake, Antarctica. Image credit: © Rob ‘Angry’ Cullen.
Deep Lake is a 36-m deep lake located about 5 km from the Australian Davis Station in the Vestfold Hills of Antarctica.
The lake became isolated from the ocean 3,500 years ago by the Antarctic continent rising, resulting in a saltwater ecosystem that remains liquid in extreme cold.
“The lake has the distinction of being the least productive lake ever recorded, with very little able to grow in it,” said senior author Prof Rick Cavicchioli from the University of New South Wales.
Prof Cavicchioli’s team took water samples from the lake at depths of 5, 13, 24 and 36 m, and studied the entire genetic sequence of the microbes living there, to work out how they had evolved to cope with the extremely harsh conditions.
Deep Lake’s microscopic inhabitants are dominated by haloarchaea, a group of microbes known to be promiscuous, swapping DNA between themselves. These extremophile microbes require high salt concentrations to grow and are naturally adapted to conditions – at minus 20 degrees Celsius – that would prove lethally cold to other organisms.
“But our research shows these ones swap much more genetic material with each other than has been observed in the natural environment before. Long stretches of virtually identical DNA are exchanged between different genera, not just species,” Prof Cavicchioli said.
“Despite this rampant gene swapping, the different species are maintained and can co-exist because they have evolved to exploit different niches and consume different food sources.”
Some, for example, consume proteins in the water; others consume sugars like glycerol, from algae living on the lake surface. It is estimated the haloarchaea grow very slowly in the lake, with only about six generations produced a year.
“Research on extremophiles could have industrial applications,” Prof Cavicchioli added.
“Enzymes from cold-adapted microbes could have significant value. Their high activity in cold temperatures could provide reduced energy costs for processes that would otherwise require heating, such as cleaning, or which must be carried out at cold temperatures, such as food production or bioremediation of cold, contaminated sites.”
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Bibliographic information: Matthew Z. DeMaere et al. High level of intergenera gene exchange shapes the evolution of haloarchaea in an isolated Antarctic lake. PNAS, published online September 30, 2013; doi: 10.1073/pnas.1307090110
