Antarctic Brine Found To Harbor Ancient Microbes
November 27, 2012

Lake Vida In Antarctica Is Home To Ancient Bacteria

April Flowers for - Your Universe Online

A pioneering new study, which included scientists from the Desert Research Institute (DRI), The University of Illinois at Chicago (UIC), and Michigan State University among others, has revealed for the first time a viable community of bacteria that survives and ekes out a living in a dark, salty and subfreezing environment. This community is beneath over 65 feet of ice in one of Antarctica's most isolated lakes; Lake Vida.

The largest of several unique lakes found in the McMurdo Dry Valleys, Lake Vida contains no oxygen. The lake, which is mostly frozen, possesses the highest nitrous oxide levels of any natural body of water on Earth. The waters of Lake Vida are approximately six times saltier than seawater. This briny liquid, which has high concentrations of ammonia, nitrogen, sulfur and supersaturated nitrous oxide, percolates throughout the icy environment that has an average temperature of minus 13.5 degrees centigrade (8 degrees Fahrenheit).

"This study provides a window into one of the most unique ecosystems on Earth," said Dr. Alison Murray, molecular microbial ecologist and polar researcher for the past 17 years, who has participated in 14 expeditions to the Southern Ocean and Antarctic continent. "Our knowledge of geochemical and microbial processes in lightless icy environments, especially at subzero temperatures, has been mostly unknown up until now. This work expands our understanding of the types of life that can survive in these isolated, cryoecosystems and how different strategies may be used to exist in such challenging environments."

A surprisingly diverse and abundant assemblage of bacteria that can survive without a present-day source of energy from the sun thrives despite the extremely cold, dark and isolated nature of the briny habitat. The brine and its inhabitants have been isolated from outside influences for more than 3,000 years, according to previous studies of Lake Vida.

The team, including Dr. Peter Doran of UIC, developed stringent protocols and specialized equipment for their field campaigns in 2005 and 2010. The goal was to sample the lake brine while avoiding contaminating the pristine ecosystem. They worked under secure, sterile tents on the lake's surface to keep the site and equipment clean. They drilled ice cores, collected samples of the salty brine in the lake ice, and assessed the chemical qualities of the water to ascertain its potential for harboring and sustaining life. They also described the diversity of the organisms detected.

On the surface of the Earth, water fuels life and plants use photosynthesis to derive energy. At the thermal vents at the bottom of the ocean, in contrast, chemical energy released by hydrothermal processes support life out of reach of the sun's rays.

Chemical reactions between the brine and the underlying iron-rich sediments generate nitrous oxide, nitrates, nitrites, and molecular hydrogen, according to geochemical analysis performed by the team. These may provide the chemical energy needed to support the diverse microbial life in the brine.

"It's plausible that a life-supporting energy source exists solely from the chemical reaction between anoxic salt water and the rock," explained Dr. Christian Fritsen, a systems microbial ecologist and Research Professor in DRI's Division of Earth and Ecosystem Sciences.

"If that's the case," echoed Murray. "This gives us an entirely new framework for thinking of how life can be supported in cryoecosystems on earth and in other icy worlds of the universe."

According to Murray, further research is already underway to analyze the abiotic, chemical interactions between the Lake Vida brine and the sediment. In addition, they are investigating the microbial community by using different genome sequencing approaches. The results of these studies could help explain the potential for life in other salty, cryogenic environments beyond Earth.

"It's an extreme environment — the thickest lake ice on the planet, and the coldest, most stable cryo-environment on Earth," Nathaniel Ostrom, Michigan State University zoologist, said. "The discovery of this ecosystem gives us insight into other isolated, frozen environments on Earth, but it also gives us a potential model for life on other icy planets that harbor saline deposits and subsurface oceans, such as Jupiter's moon Europa."

Lake Vida's brine represents a cryoecosystem that is suitable and accessible as an analog for the soils, sediments, wetlands, and lakes underlying the Antarctic ice sheet. These areas are just beginning to be explored by other polar research teams.

The National Science Foundation and NASA funded the study which recently published in the journal Proceedings of the National Academy of Sciences.