A tiny bacterium has been coaxed back to life after spending 120,000 years buried three kilometres deep in the Greenland ice sheet.
Officially named Herminiimonas glaciei, the bug consists of rods just 0.9 micrometres long and 0.4 micrometres in diameter, about 10 to 50 times smaller than the well-known bacterium, Escherichia coli.
"What's unique is that it's so small, and seems to survive on so few nutrients," says Jennifer Loveland-Curtze of Pennsylvania State University, whose team has described the new species.
She speculates that thanks to its tiny dimensions, it can survive in minute veins in the ice, scavenging sparse nutrients that were buried along with the ice. It also has extensive tail-like flagella to help it manoeuvre through the veins to find food.
"Along with the snow, you get dust, bacterial cells, fungal spores, plant spores, minerals and other organic debris," says Loveland-Curtze. "So we postulate that it lives in these microniches in the ice."
Coaxed back to life
Researchers in the team coaxed it back to life by keeping it at 2 °C for 7 months, then at 5 °C for a further four-and-a-half months, after which they saw colonies of very small purplish-brown bacteria.
Loveland-Curtze speculates that similar microbes may have evolved in the ice on other planets and moons, such as the ice at the poles of Mars and the ice-covered ocean on Europa, one of Jupiter's moons.
"All we can say is that because ice is the best medium to preserve nucleic acids, other organic compounds and cells, the potential for finding them in these environments is quite high because of the cold," says Loveland-Curtze. "It gives us hope that if something is there, we can locate it."
The oldest known ice on Earth yielded a bacterium that grew after 8 million years.
Journal reference: International Journal of Systematic and Evolutionary Microbiology (DOI: 10.1099/ijs.0.001685-0).
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