In either case, the study suggests the lake could support a microbial population, despite a million years of isolation from the atmosphere, according to the article in Science.
The MSU-led group was not able to determine whether the microbes were alive or merely trapped in an ancient icy grave.
"They could have been alive, but growing so slowly that we could not detect growth rates using our protocols," Priscu said. "If alive, I think they are in a maintenance mode of metabolism, rather than one of active growth."
Priscu and his teams have found microbes growing in other Antarctic frozen lakes, but none nearly as deep as Lake Vostok. Microbes are known to hang out in other extreme environments, such as hot vents along undersea trenches, deep in the earth's subsurface and in geothermal pools like those in Yellowstone National Park.
And if microbes exist on other planets, such as in the frozen ocean thought to exist on Jupiter's moon Europa, finding them could be similar to hunting for them in Lake Vostok, the scientists say.
"Similar to Lake Vostok accretion ice, this ice may retain evidence for life, if present, in the europan ocean," the scientists wrote.
Internal energy from the planet could drive an energy system independent of the sun and possibly sustain life in really extreme environments, said MSU earth sciences professor and co-author David Mogk.
"I think the message is really, 'Life is where you find it'," Mogk said. "If you find it under nearly 4,000 meters of ice, I mean, that's pretty staggering."
In addition to searching for bacteria, the group studied the ice's unique crystal structure and mineral composition using aspecialized scanning electron microscope.