A bacterium that sat dormant in a frozen pond in Alaska for 32,000 years has been revived by NASA scientists. Once scientists thawed the ice, the previously undiscovered bacteria started swimming around on the microscope slide. The researchers say it is the first new species of microbe found alive in ancient ice. Now named Carnobacterium pleistocenium, it is thought to have lived in the Pleistocene epoch, a time when woolly mammoths still roamed the Earth.
NASA astrobiologist Richard Hoover, who led the team, said the find bolsters the case for finding life elsewhere in the universe, particularly given this week’s news, broken by New Scientist, of frozen lakes just beneath the surface of equatorial Mars. The team initially set out to find bacteria that thrived at extremely low temperatures, so it was a surprise to find organisms that tolerated the cold, but preferred room temperature. “I think the most important thing from this observation is that microorganisms can be preserved in ice for long periods of time,” Hoover told New Scientist.
He retrieved the bacteria from a tunnel in the Alaskan permafrost, carved by the US Army’s Cold Regions Research and Engineering Laboratory. Walking through the tunnel, Hoover saw a fossilised mammoth tusk protruding from one side and an ancient jawbone on the other. The bacteria came from a cross-section of a preserved pond. The bottom of the pond was a brownish hue, which Hoover thought might be caused by diatoms – single-celled algae. “Frankly, I was disappointed that there weren’t any diatoms at all,” he says. Instead, he saw a host of pigmented bacteria that started swimming as soon as the ice melted. He took the samples back to Marshall Space Flight Center in Alabama, US, and cultured the samples. Initially, the team thought it might be an existing bacterium, but gene sequencing revealed it as a new species.
Another group of researchers from West Chester University in Pennsylvania, US, claimed in 2000 that they had isolated a 250-million-year-old bacterium. But other scientists disputed that the microbes could so very old. For example, those particular microbes like salty environments. And salt deposits tend to have water moving through them, potentially bringing contamination, says Robert Hazen, a geophysicist with the Carnegie Institution of Washington and president of the Mineralogical Society of America. “The fact you have extracted microbes from the salt doesn’t really tell you the microbes are as old as the salt,” he says. While Hazen says that 250-million-year-old microbes seemed unlikely, “I wouldn’t be surprised at microbes that are a few tens of thousands of years old”.
Journal reference: International Journal of Systematic and Evolutionary Microbiology (vol 55, p 473)
March 15, 2005
Original web page at New Scientist