US researchers claim to have revived bacteria that have spent the last 250 million years in suspended animation. David Adam investigates.
USresearchers claim to have revived bacteria that have spent the last 250 million years in suspended animation. If true, the bugs smash the accepted record for the oldest living creatures ever discovered, previously held by bacteria a mere 25--40 million years old.
The discovery raises the chances of life being able to survive long enough to travel between planets -- our entire galaxy has completely rotated since these particular bugs last wriggled.
"The potential implications are profound," says microbiologist John Parkes at Bristol University, UK. "If bacteria can survive for this length of time [then] why should they die at all?"
The secrets to (almost) eternal life, it seems, are spores. When times are hard, bacteria and yeast shut down just about every function and form a tough, resilient structure. Such spores have been isolated -- and brought back to life -- from 118-year-old cans of meat and have even been used to recreate a 166-year-old bottle of beer.
Russell Vreeland, of West Chester University, Pennsylvania, and his colleagues now say they have revived bacterial spores from salt crystals that formed in Texas before dinosaurs appeared on Earth.
The Bacillus bacteria that were isolated by the team like to live in salt water. So Vreeland's team suggests that the bugs formed spores and the salt water then crystallized around them, trapping them in a tiny brine pocket some 250 million years old, from which they have now been freed. The researchers report their findings in Nature1.
Similar claims have been made and rejected before, and other researchers will take some convincing over these. Most important of all is the question of possible contamination by modern bugs. To prevent this, the group sterilized the surface of the crystal samples with strong acid and alkali before bringing the spores out. This reduces the chance of contamination, they say, to less than one in one hundred million.
Others warn that the bacteria could have made the samples their home far more recently, but this is impossible if the salt crystal formed around the spores as the team claims. "Delicate crystal structures and sedimentary features indicate that the salt has not recrystallized since formation," they say.
To help avoid confusion over contamination, Vreeland's team copied, as far as possible, the procedure used recently to isolate bacterial spores from a bee preserved in amber up to 40 million years old2. In this case, researchers could even extract and analyse DNA from the spores, showing the bugs to be another Bacillusstrain of bacteria.
The new study offers the strongest evidence yet of very-long-term microorganism survival, Parkes says. Still, other researchers will have to repeat the experiments before the results are fully accepted, he concedes -- and similar studies in different salt deposits are required.
Vreeland,R. H., Rosenzweig, W. D. & Powers, D. W. Isolation of a 250 million-year-old bacterium from a primary salt crystal. Nature 407, 897 - 900 2000.
Cano,R. J. & Borucki, M. Revival and identification of bacterial spores in 25 to 40 million year old Dominican amber. Science 268, 1060 - 1064 1995.
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Adam, D. Hardcore hibernation. Nature (2000). https://doi.org/10.1038/news001019-9