Revived Microbe Predates T-Rex, Scientists Say
From a spore locked inside a salt crystal before the dinosaurs evolved, scientists have revived what they believe is a microbe that lived more than 250 million years ago.
The ability of a living organism--even a simple, single-celled one--to survive in suspended animation for so many eons could be evidence that life forms can live long enough to drift from planet to planet and might even survive today in ancient subterranean salt deposits on Mars, several experts speculated.
Follow-up studies will be needed to confirm the finding, announced by a research team at West Chester University outside Philadelphia and made public today in Nature. The newly found spore is similar to two species of modern bacteria but appears to have a number of genetic differences.
Environmental biologists Russell H. Vreeland and William D. Rosenzweig discovered the salt crystal, with its living time capsule, by sorting through 220 pounds of samples taken from an air shaft 1,850 feet below the ground at the U.S. Energy Department’s Waste Isolation Pilot Plant about 30 miles east of Carlsbad, N.M.
The extensive salt beds formed when New Mexico was awash with a primordial inland sea. Geologic dating pegs the formation as about 250 million years old. The scientists have deduced that the spore is the same age.
If proved, the finding would be a startling demonstration of the extremes that life can endure.
Bacteria have been found thriving in boiling springs and in the deep freeze of Antarctic ice. They can live without light or oxygen, in radioactive waste and toxic dumps, amid crushing pressure underwater or deep underground. And in recent years, researchers have resuscitated spores from a 100-year-old can of meat, a 166-year-old bottle of ale, even from the belly of a bee trapped in amber more than 25 million years ago.
But the newest finding would extend the reach of a single life span into unfathomable depths of time--to an age when even the continents had not yet taken their current shapes. Secure in its capsule, the spore apparently survived at least three mass extinctions that wiped out 95% of all life forms on Earth.
“Given the care [the researchers] took to avoid contamination, their results are the best evidence yet for the extremely long-term survival of microorganisms,” said R. John Parkes, an expert in geo-microbiology at the University of Bristol in England. “The potential implications are profound. For instance, can spores effectively be immortal?”
However, other experts greeted the new report with considerable skepticism, noting that the researchers can only infer the age of the sample and that there is no way to prove directly that the microbe is so ancient. They also worry that the salt sample may have leaked or been contaminated. They wonder what energy source could have sustained a cell for so long, even if it were dormant.
“It would seem pretty unlikely for an organism to sit in a state of suspended animation for 250 million years,” said paleobiologist William Schopf, director of UCLA’s Center for the Study of Evolution and the Origin of Life. Even so, he said, the finding is “very, very interesting.”
NASA astrobiologist Michael Meyer in Washington cautioned, “Proving that something is actually 250 million years old and viable is a difficult problem, and it may not be resolvable. It is a tough nut to crack.
“If it is true,” Meyer said, “the implications for astrobiology are pretty important.”
Recognizing that theirs is an extraordinary claim, Vreeland and Rosenzweig said they went to unusual lengths to ensure that the crystals were properly isolated and the spore revived without being contaminated by contemporary life forms.
Working in a special biological containment facility at their West Chester laboratory, the researchers searched for crystals that had not changed since they first formed when the sea evaporated so many eons ago. In all, they found 56 crystals that still seemed sealed and pristine from that primordial era.
“We started with 220 pounds of salt,” Vreeland said. “We have gone through it crystal by crystal and selected only the ones we felt we could defend as to its age.”
To protect against contamination they bathed each crystal in acid, then radiated it for hours with sterilizing ultraviolet light, they said. From microscopic bubbles in those crystals, they extracted minute amounts of fluid, then cultured the fluid in lab dishes.
The type of bacteria they found in the fluid is similar to a modern strain in the Dead Sea. A preliminary genetic comparison suggests that there are about 45 differences between the DNA of that modern organism and that of the type found in the crystal, the researchers said. That is what would be expected if the two had been separated for about 250 million years, with one type continuing to evolve while the other remained the same.
“Having an organism that we can be reasonably certain was present in the Permian era [250 million years ago] is almost the next best thing to being there,” Vreeland said. “We can ask biological questions that we can’t ask a fossil.
“As a man of faith, it amazes me that there is a supreme being that would protect a bacterial spore,” said Vreeland, a Methodist. ‘To consider that in the time this helpless spore has been encased, continents have moved, that mountain ranges have been built and destroyed--I think it is pretty impressive.”
Astrobiologists were intrigued by the discovery, because there are believed to be similar salt deposits on Mars. If a microbe can survive so long on Earth, they say, similar spore-forming organisms might lurk in those deposits beneath the surface of the red planet.
Geobiologist James Fredrickson of the Pacific Northwest National Laboratory in Richland, Wash., has been conducting similar studies on bacteria in ancient salt crystals with colleagues at the University of Missouri and Princeton University. He does not dismiss the new report out of hand, nor does he underestimate the difficulty of the task.
“Nobody really knows how long a spore can survive,” Fredrickson said, “because you can’t run an experiment for thousands of years to find out.”
