Recent laboratory tests with primitive microbes from an Antarctic lake have revealed they can form a chemically linked unit called a biofilm. The finding marks the first time this phenomenon has been detected in the Antarctic species of extremophiles.

    "The cold-adapted microorganisms studied in this investigation have not been observed to form biofilms in the past, and so the observation of biofilms in the cold was a surprise," said Shiladitya DasSarma of the University of Maryland Biotechnology Institute, part of the Maryland Astrobiology Consortium.

    Scientists with the consortium focused on two species of cold-adapted microbes. One, called Halorubrum lacusprofundi, is highly salt-tolerant. The other, Methanococcoides burtonii, can live without oxygen and thrives on methane.

    Both microbes are types of Archaea, one of the three major types of life along with bacteria (another class of microbes) and eukaryotes (a group that includes animals, plants, fungi and protists, e.g. paramecium, algae, protozoa and slime molds).

    Archaea might be able to survive in many places in the universe beyond Earth, including some of the more than 180 extrasolar planets detected in the past decade, or on their terrestrial moons.

    The team, led by DasSarma grew the microbes and found they survived and reproduced at 30 and 28 degrees Fahrenheit (about -1 and -2 degrees Celsius), respectively, just below the freezing point of water.

    "We have extended the lower temperature limits for these species by several degrees," DasSarma said. "We had a limited amount of time to grow the organisms in culture, on the order of months. If we could extend the growth time, I think we could lower the temperatures at which they can survive even more."

    H. lacusprofundi was chosen for the experiments because they could possibly thrive in the salty water thought to exist below Mars' surface, which can remain liquid at temperatures well below 32 degrees Fahrenheit. M. burtonnii was chosen because it could survive on a planet lacking oxygen, such as Mars.

    The lab-grown archaea also adapted to the cold by aggregating to form biofilms or microbial mats, like the slimy plaque that accumulates on your teeth. Aggregating to form a mat or biofilm allows microbes to share nutrients and genetic material.

    (Agencies)