Looking for life in all the worst places.

Thriving microbial communities have turned up in one of the coldest spots on Earth--some 6 feet under the permanent ice cover of lakes in Antarctica.

In the McMurdo Dry Valleys, annual temperatures drop as low as -45 [degrees] F, and precipitation amounts to only 4 inches a year. The summer sun, however, warms grit stuck in the ice and creates small, enclosed slushy worlds. These complex microbial communities include cyanobacteria that photosynthesize even in the dim light available deep in the ice.

During the dark of winter, the ice freezes solid again, and the communities shut down until the next year. "They're really trapped in the ice," says Stephen J. Giovannoni of Oregon State University in Corvallis. He and his colleagues describe their discovery in the June 26 Science.

Life goes on in some pretty cold places, note Roland Psenner and Birgit Sattler at Innsbruck University in Austria. In an accompanying commentary, they point out that brine in sea ice harbors algae and crustaceans and that bacteria inhabit the slush on lakes high in the Alps. But even by these standards, Psenner and Sattler view Antarctic ice conditions as "extreme."

Life on ice: Close-up of an Antarctic cyanobacteria colony some 35 micrometers across.