Scientists have revived microbes found in 100-million-year-old sediment from deep beneath the ocean floor. The experiment sheds new light on where life on Earth can be found – and how stable it can be.
According to a new study published in the journal Nature Communications, the microbes found buried under the sea have lasted up to 101.5 million years. Sediments do not have the energy needed to allow cells to sustain themselves, but scientists were still able to revive communities.
It is a mystery how the microbes were able to survive the harsh conditions of their environment – and it is unclear how long they can live. The researchers said they may be the oldest known organisms on the planet.
Scientists at the Japan Marine Land Science and Technology Agency analyzed sediment samples found approximately 12,140 to 18,700 meters below the ocean surface in the South Pacific Gyre, a system of rotating currents located in the Pacific Ocean. The center of the South Pacific Gyrus contains the “ocean of inaccessibility pole,” the site on Earth farthest from all land – the lowest productivity part of the entire ocean.
The area has little food, but it contains a lot of oxygen deep beneath the sea floor. Sediment layers, collected during a 2010 expedition, were deposited over a period from 13 million to 101.5 million years ago.
Inside the sediment, scientists found marine microbes: small, single-celled microorganisms that make up the bulk of the total mass of living creatures in the ocean. Trapped in the sediment layers, they could barely move or eat.
The researchers wanted to know if life could exist in such a nutrient-poor environment.
Back in the lab, researchers were able to raise germs from their long quarters. They gave ancient samples carbon and nitrogen substrates, to test if they were feeding and dividing cables into more cells.
Over a period of 68 days, most of the nearly 7,000 cells responded rapidly to the new conditions, multiplying by four orders of magnitude – even in older samples. The researchers said aerobic bacteria dominated the experiment.
“What we found is that life lasts all the way, from the sea to the basic rock basement,” said orthography and study co-author Steven D’Hondt in a video news release from the University of Rhode Island. “Those organisms are not only alive in the deepest, oldest sediment, but they are capable of growing and dividing.”
“It is surprising and biologically challenging that a large proportion of microbes can be resurrected from a very long time of burial or trapping in extremely low nutrient / energy conditions,” lead author Yuki Morono told Reuters.
Research shows that microbes can survive for previously impenetrable durations if sediment accumulates at a very slow rate, blocking oxygen over time.
Through further experiments, researchers now hope to determine how microbes were able to survive for millions of years.
“The most exciting part of this study is that it basically shows that there is no limit to life in the Earth’s old ocean sediment,” D’Hondt told Reuters. “Keeping full physiological ability for 100 million years in starvation isolation is an impressive impression.”