Researchers have successfully revived dormant microbes trapped in an apparently lifeless area of the seabed for more than 100 million years.
A team of scientists from Japan and the United States was looking to see if microscopic life survives in less hospitable conditions below the sea floor of the Pacific Ocean.
“We wanted to know how long the microbes could maintain their lives in the absence of food,” said microbiologist Yuki Morono of the Japan Earth and Sea Science and Technology Agency, who led the study.
They got their answer: Microbes that had been trapped in the seabed sediments deposited 100 million years ago could be revived with the right food and a little added oxygen.
Which is awesome. The pressure is immense for microbes on the sea floor, all that water accumulated on top of the sea floor. Not to mention a lack of oxygen, few essential nutrients, and paltry energy supplies.
When life is trapped in other high-pressure environments, fossils generally form after a million years or more, but these powerful microbes were very much alive.
“We knew there was life in deep sediments near continents where there is a lot of buried organic matter,” said Morono’s colleague, geomicrobologist Steven D’Hondt of the University of Rhode Island. “But what we found was that life extends into the depths of the ocean from the sea floor to the underlying rocky basement.”
The soil in which the microbes were trapped was taken from a 2010 expedition to the South Pacific Gyre, an apparently lifeless area at the center of eddy ocean currents in eastern Australia, known as one of the most limited parts in food and deficient in life. from the ocean (and a garbage vortex, with all the plastic pollution that accumulates on the surface).
As part of a 2010 expedition aboard the JOIDES Resolution drilling vessel, the team extracted sediment cores that were found at depths of up to 75 meters (250 feet) below the sea floor, which is nearly 6 kilometers (nearly 20,000 feet) below the ocean surface.
They took samples of ancient pelagic clay, which accumulates in the deepest and most remote parts of the ocean, and much younger and calcareous, between 4.3 and 13 million years old.
They found microbes that consume oxygen (and dissolved oxygen) through each layer of the nuclei, from top to bottom, and at each site they sampled in the South Pacific turn. But the microbes were hiding in very low numbers.
On board the ship, samples were taken of the sediment cores to see if the energy-deprived microbes had retained their “metabolic potential” and could feast and multiply.
The ancient microbes received an oxygen boost and were fed traceable substrates containing carbon and nitrogen, their food of choice, before the glass vials were sealed, incubated, and only opened after 21 days, 6 weeks, or 18 months .
Even in the oldest sediments sampled, the researchers were able to revive up to 99 percent of the original microbial community.
“I was skeptical at first, but we found that up to 99.1 percent of the microbes in sediment deposited 101.5 million years ago were still alive and ready to eat,” Morono said.
After their long incubation, the microbial communities were classified according to their genes. The researchers reported that the seafloor soils were dominated by bacteria, but not the spore-forming type, meaning they were ready to grow as soon as they were given the right food.
Some microbes quadrupled in number and consumed available carbon and nitrogen 68 days after incubation.
“It shows that there are no limits to life in the old sediment of the world ocean,” said D’Hondt. “In the oldest sediment we have drilled, with the least amount of food, there are still living organisms, and they can wake up, grow and multiply.”
It is not just deep in the oceans that microbes have shown how resilient they can be. Scientists have also found microbes that live in extreme conditions in Antarctica, as well as the driest deserts.
The study is published in Nature’s Communications.
.
