From the belly of a honeybee that bumbled when saber-toothed cats prowled the planet, two researchers have brought back to life dormant prehistoric bacteria that were alive more than 25 million years ago.
Preserved inside an insect trapped in the sap of a flowering tree, these living fossils are the first proof that any organism of such antiquity can be revived, according to research made public today in the journal Science.
Thriving now in laboratory culture dishes under lock and key in San Luis Obispo, the ancient bacteria promise new insights into the pace of evolution and may even prove to be a source of potentially useful new medicines, the researchers said. A biotechnology company is already trying to patent the prehistoric microbes.
In addition to the work reported today, microbiologists Raul Cano and Monica Borucki at Cal Poly San Luis Obispo say they have also revived several hundred specimens of bacteria from ancient bees, gnats and beetles trapped in amber up to 135 million years old, in work evocative of the science fiction novel "Jurassic Park." Those findings have not yet been reviewed by other scientists.
At least half of all the specimens appear to be different, as yet unidentified, species. All had survived the millennia trapped in amber by hibernating inside tough protective spores, which Cano was able to reawaken in his laboratory. They all appear to be harmless species.
"The point is these organisms may represent a brand-new source of pharmaceutical drugs and industrial enzymes," Cano said.
"They are producing enzymes and antibiotics that are different than modern ones," he said. "There may be a potential for finding antibiotics that will inhibit the growth of some modern organisms that are resistant to modern antibiotics."
Other researchers were cautious about such claims, saying the discovery of a useful natural antibiotic from ancient bacteria is about as likely as winning the lottery. They also were concerned that what appear to be ancient bacteria may simply be contamination from more modern molecules.
They acknowledged that Cano and Borucki appear to have taken extraordinary precautions to avoid contamination by modern bacteria, but some scientists were eager to see the work duplicated by other laboratories. Cano revived the first of the ancient bacteria in 1991 and has spent the intervening years verifying his discovery.
"There are always reservations about something like this," said Peter Setlow, a specialist in bacterial spores at the University of Connecticut Health Center. "It would be really exciting if it were true. It is crucial that other people be able to repeat this.
"To my way of thinking, they looked in the right place for the right kind of organism," Setlow said. "The kind of bacteria found in the guts of present-day insects is very much like the one in the pieces of amber."
Researchers were especially excited by the idea that such bacteria might provide a way to calibrate the so-called molecular clock that sets the pace at which the evolution of life has unfolded.
Unlike the remains of plants and animals, the molecules that make up DNA do not leave any fossil imprints that scientists can examine.
Until now, most knowledge about the molecular processes that underlie evolutionary change has come from comparisons of genes taken from living species, said University of Munich biologist Svante Paabo. Researchers have to venture their best educated guess about how those genes changed over time.
With the bacteria Cano revived--a kind of microbe called Bacillus sphaericus-- scientists will have an unprecedented opportunity to study evolution by comparing living fossils with their modern descendants.
"It has always been felt that evolution proceeds at some finite rate," Setlow said, "but there is no ancient organism that we can use as a benchmark. Well, now we have one--a frozen picture of what it was like 30 million years ago. So we can calibrate the clock."
The search for ancient DNA has led some scientists to scavenge for dinosaur bones in coal mines, and others to tap the fossil bone marrow of Tyrannosaurus rex in what so far have been futile efforts to extract genetic material from those prehistoric creatures.
Scientists have had better success with other life forms.
From human brains 3,000 years old, from fossil magnolia leaves 17 million years old, and from insects like the bee trapped in amber tens of millions of years ago, scientists have obtained strings of the spiral DNA molecules responsible for life. They even got DNA from bones of a saber-toothed cat that died 14,000 years ago in the La Brea tar pits.
But until now, the idea that scientists could revive an actual organism that lived so long ago was safely in the realm of science fiction. By reviving the dormant one-celled creatures, Cano and Borucki have taken the search to a new level.
Experts say that fossils preserved in amber are well-suited for molecular studies because the fossilized tree sap isolates any organic tissue from air, water and other agents of decay. By forming thick, protective shells of protein, the bacteria increased their own chance of survival while they were dormant.
Cano extracted the spores from the abdomen of the ancient bee after sterilizing the exterior of the amber in which it was encased. When he bathed the sample in nutrients, the bacteria began to grow, he said.
By comparing genetic sequences of ancient and modern bacteria, Cano was able to show that the bacteria in his lab dishes had grown from the prehistoric spores.
He determined the age of the bacteria by dating microscopic fossils from the rocks in the Dominican Republic where the amber was found.
A contract between Cal Poly and a company called Ambergene, which was formed to commercialize Cano's work, provides for royalties to be paid to the school if any of the bacteria turn out to be profitable.
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Reviving Prehistoric Microbes
Scientists at Cal Poly San Luis Obispo have discovered that bacteria millions of years old can be brought back to life. They revived bacterial spores found inside insects that had been trapped in amber more than 25 million years ago.
1. A stingless bee, attracted perhaps by the lure of a flower, was caught in sticky tree sap that later fossilized into amber.
2. As the amber dried, bacteria inside the bee formed themselves into protective spores, which can survive extreme dehydration and lack of food. Until now, the longest any spore was know to have survived was 70 years.
3. Scientists extracted the spores from the amber, bathed them in nutrients and the bacteria began to grow again. Researchers are now testing the bacteria to see if they produce useful antibiotics or other medicinal compounds.
Sources: Science, Cal Poly San Luis Obispo