US scientists find ancient microbes in salty, ice-sealed Antarctic lake

U.S. scientists have discovered abundant and diverse metabolically active bacteria in the brine of an Antarctic lake sealed under more than 65 feet (19.8 meters) of ice, according to a study published Monday in the Proceedings of the National Academy of Sciences. The finding is surprising because previous studies indicate that the brine has been isolated from the surface environment -- and external sources of energy -- for at least 2,800 years, according to the study. "This provides us with new boundary conditions on the limits for life," said Peter Doran, a study author and professor at the University of Illinois at Chicago. "The low temperature or high salinity on their own are limiting, but combined with an absence of solar energy or any new inputs from the atmosphere, they make this a very tough place to make a living." The researchers drilled out cores of ice, using sanitary procedures and equipment. They collected samples of brine within the ice and assessed its chemical qualities and potential for sustaining life. They found that the brine is oxygen-free, slightly acidic, and contains high levels of organic carbon, molecular hydrogen, and both oxidized and reduced compounds. The findings were unexpected because of the extremely salty, dark, cold, isolated ecosystem within the ice. "Geochemical analyses suggest that chemical reactions between the brine and the underlying sediment generate nitrous oxide and molecular hydrogen," said study author Fabien Kenig. "The hydrogen may provide some of the energy needed to support microbes."