THE common ancestor of all living things was able to survive in almost
boiling water, claims Akihiko Yamagishi of the Tokyo College of Pharmacy.
His team worked out the 鈥渁ncestral鈥� structure of a commonly occurring enzyme,
3-isopropylmalate dehydrogenase, by comparing the versions of it found in
today鈥檚 bacteria. The researchers then modified a high-temperature bacterium,
Sulfolobus, to produce the ancestral enzyme. They found that the enzyme
withstood temperatures as high as 99 掳C鈥攖hree degrees higher than the
version normally found in Sulfolobus, Yamagishi told a recent meeting
of the Molecular Biology Society of Japan.
Many researchers, however, believe life on Earth began in a low-temperature
environment. 鈥淭he fact that we have a high-temperature ancestor suggests there
was an evolutionary bottleneck,鈥� says Yamagishi. A disaster such as an asteroid
collision may have killed off low-temperature bacteria, he suggests.
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