Scientists have revived microbes found in 100-million-year-old sediment deep beneath the seabed. The experiment sheds new light on where life can be found on Earth – and how resilient it can be.
According to a new study published in the journal Nature Communications, microbes found buried under the seabed persist for up to 101.5 million years. Sediments do not have the energy needed to sustain cells, but scientists were still able to revitalize communities.
It is a mystery how microbes were able to survive the harsh conditions of their surroundings – and it is not clear how long they can live. Scientists say they could be the oldest known organisms on the planet.
Researchers at the Japan Marine Science and Technology Agency analyzed samples of sediments located approximately 12,140 to 18,700 feet below ocean level in the South Pacific Gyre, a system of rotating currents located in the Pacific Ocean. In the middle of the South Pacific Gyre is the “ocean column of inaccessibility”, the place on Earth furthest from all the country – the lowest productivity of the entire ocean.
This area has little food, but a lot of oxygen is hidden deep below it. Sediment layers harvested during the 2010 shipment were deposited from 13 million to 101.5 million years ago.
Scientists have found marine microorganisms in the sediment: small single-celled microorganisms that make up the vast majority of the total mass of living creatures in the ocean. Trapped in layers of sediment could barely move or eat.
Researchers wanted to know if life could exist in a nutrient-poor environment.
Back in the lab, the scientists were able to wake the microbes from their long sleep. They gave the old samples carbon and nitrogen substrates to test whether they were fed and divided into multiple cells.
Over 68 days, the vast majority of the nearly 7,000 cells responded rapidly to the new conditions and multiplied by four orders of magnitude – even in the oldest samples. The researchers claim that the experiment was dominated by aerobic bacteria.
“We’ve found that life evolves from the seabed to the bedrock,” said Steven D’Hondt, an oceanographer and co-author of the study, in a video release. “These organisms are not only alive in the deepest, oldest sediment, but they are able to grow and divide.”
“It’s surprising and biologically challenging that much of the microbes could be recovered from a very long period of burial or capture in extremely low nutritional / energy conditions,” lead author Yuki Morono told Reuters.
Research suggests that microbes may survive previously incomprehensible times if sediment accumulates very slowly and scavenges oxygen over time.
Through further experiments, scientists now hope to determine how microbes have survived millions of years.
“The most interesting part of this study is that it basically shows that life in the old sediment of the Earth’s ocean does not exist,” D’Hondt told Reuters. “Maintaining full physiological capacity for 100 million years in starvation is an impressive act.”