A prominent molecular biologist says he has restored dormant, 30 million-year-old bacteria to life, a feat so astonishing that, if confirmed, would force scientists to re-examine long-held notions about the temporal limits of life.
A report of the achievement is to be published today in the journal Science, but even before its publication, scientific skeptics familiar with the work were labeling the claim implausible and probably the result of accidental contamination of laboratory specimens.
Nevertheless, Raul J. Cano, a microbiologist at California Polytechnic State University at San Luis Obispo, is confident that he has revived bacteria that date from tens of millions of years ago.
He said he had accomplished the feat by extracting bacterial spores, a form in which the microbes are in suspended animation, from the stomachs of ancient bees embedded in tropical amber and growing the bacteria in a culture in a laboratory dish. He said he had revived more than 100 types of ancient bacteria.
Although some investigators have recovered what they believe to be fragments of the genetic material DNA from preserved biological tissue millions of years old, the notion that it might be possible to revive an entire organism of such great age has been generally dismissed as science fiction.
Even a one-celled organism like a bacterium is vastly more complex and, presumably, more vulnerable to the ravages of time than is a chemical compound like DNA, it was believed.
A living organism is subject to starvation, extremes of temperature, chemical attack, oxidation and assaults by microorganisms and enzymes. It seems almost incredible that a living organism subjected to all that could survive millions of years, even in suspended animation.
But scientists have long known that bacteria have some potent defenses. When bacteria are subjected to extremely hostile, but not fatal, conditions, they often encapsulate themselves in thick layers of protein and shut down their metabolism. They become spores, withstanding the rigors of desiccation, heat and cold.
Although spores hundreds of years old have been found, rehydrated, nourished and restored to life as bacteria, the revival of spores millions of years old was widely considered impossible.
Dr. Cano is well known among molecular biologists for the revolutionary research conducted by a team of which he was a member.
Dr. Cano is so confident of his latest findings that he has founded a company, Ambergene Corp., in San Carlos, Calif., to develop pharmaceutical products derived from the putative ancient organisms.
Ambergene has already applied for patents for at least three of the new antibiotics he believes the bacteria have helped him to produce.
These drugs, he said, could fill therapeutic gaps created by the increasing immunity of certain disease-spreading microbes to antibiotics.
Dr. Cano said most of the ancient microorganisms he had cultured are strains of bacillus sphaericus, a harmless bacterium that is common today in soil and in the bodies of insects.
Whether or not the strains of bacillus sphaericus found in amber are essentially identical to modern bacteria remains to be seen.
Dr. Cano and his former graduate student Dr. Monica K. Borucki said that they had found slight but significant differences between the DNA of the ancient, amber-sealed bacillus sphaericus and that of its modern counterpart.
Dr. Cano said he and his colleague had taken such scrupulous precautions that accidental contamination appeared to be ruled out.
Before piercing the amber, its surface was chemically sterilized, he said, and sterile conditions were maintained during the extraction of bacteria from the bee stomachs.
In control tests using sterilized amber that contained no bees, Dr. Cano repeated his procedure, and when the resulting material was inoculated into a culture medium, no bacteria grew. The inference, he said, is that the bacteria in amber really are ancient.
The source of Dr. Cano's specimens was amber mined in the Dominican Republic and Mexico. Chunks of amber were extracted from layers of sedimentary rock that formed 25 million to 40 million years ago during the Oligocene epoch. (By comparison, the last of the dinosaurs died out 65 million years ago.)
George Poinar, a biologist at the University of California at Berkeley and a former colleague of Dr. Cano in several research projects, calls them "windows on the past."
Dr. Poinar's own study of ancient DNA extracted from amber inspired Michael Crichton to write the science-fiction dinosaur fantasy "Jurassic Park."
One leading expert, Dr. Tomas Lindahl of the Imperial Cancer Research Fund in Hertfordshire, England, who has extensively investigated the physical and chemical characteristics of DNA and its long-term stability, said in an interview that he doubted that the bacteria isolated and cultured by Dr. Cano were really ancient.
"My interest is in the DNA chemistry," he said. "I find it highly unlikely that you can recover viable bacteria from material that old. They are much more likely to be the result of human contamination. This field is full of pitfalls."