49.
The author is most probably a ______.
A. teacher
B. psychologist
C. philosopher
D. doctor
C
Imagine putting some bacteria in the freezer and taking them out millions
of years later to find that they are still alive.
That would be similar to what happened recently, when scientists brought
eight-million-year-old bacteria back to life - simply by thawing them out.
The ancient bacteria were found frozen in the world's oldest known tracts
of ice, the glaciers(冰川)of Antarctica.
Professor Bidle and his colleagues found and revived(复活)two samples of bacteria from the glacial ice.
The first was a hundred thousand years old, and the second was around eight
million years old. The eight-million-year-old bacteria were alive. But their
genes were seriously damaged from long exposure to cosmic(宇宙 )radiation, which is higher at the earth's
poles.
Most of the bacteria in the samples probably blew over from African
deserts, said Paul Falkowski, a scientist at Rutgers University.
Once the bacteria landed on the glacier's snowy surface, they combined with the
snow to form ice. "These ices are actually gene banks," he added.
As glaciers and ice caps melt as a result of increasing global warming,
large amounts of bacterial genetic material might be washed into the ocean.
These bacteria might get incorporated into today's bacteria in the ocean,
or living bacteria from the ice might also grow and have an important effect on
the ecosystem.
"How that's going to play out, we don't know," Bidle said. He
and Falkowski plan to focus their future work on how current ice melting
influences modem bacteria's genetic diversity.