An article published in the journal “Nature Communications” reports the discovery of living colonies of bacteria in sediment layers up to 101.5 million years old in the depths of the Pacific Ocean area called the South Pacific Gyre. A team of researchers led by JAMSTEC’s Dr. Yuki Morono drilled the ocean floor in an area where it’s nearly 6 kilometers deep to collect many sediment samples up to 100 meters below the ocean floor. This is the Pacific area with the lowest productivity and the least amount of nutrients available, yet the researchers found bacteria in the sediments that are millions of years old and managed to bring them back to full metabolic activity.
The South Pacific Gyre is part of the ocean currents system with the oceanic pole of inaccessibility at its center, meaning the point of the Pacific furthest from all the land. It’s an area where life conditions on the seabed are really difficult, but in recent decades life forms have been found in really extreme environments. For this reason, Dr. Yuki Morono of JAMSTEC (Japan Agency for Marine-Earth Science and Technology) and his team wondered if life forms could survive in those conditions.
Samples of the ocean floor and sediments under the ocean floor are taken for different types of research, from geological to climatic. In certain cases, the remains of life forms are also sought, as they can be fossilized in sediments, especially if the layers date back to many millions of years ago. Dr. Yuki Morono’s team drilled the seabed in an area where the depth is about 6 kilometers for about 100 meters below the seabed, finding conditions in which oxygen can penetrate down there. These are far from ideal conditions for life, yet oxygen is enough for the survival of aerobic bacteria.
To verify the state of the aerobic bacteria discovered in the sediments, the researchers tried to supply oxygen and nutrients to some samples under laboratory conditions. Various experiments have been carried out providing different nutrients. The bacteria reacted by growing and reproducing, at different rates depending on the substances supplied, showing that they’re still alive.
These surprising results pose some questions about the metabolism of these bacteria in the environment in which they were found. The colonies discovered date back to millions of years ago but what about individual bacteria? Is it possible that a living being can survive for so long in a state of stasis or close to stasis? The alternative is that the metabolism of these bacteria is very slow but still sufficient for reproduction, even in those conditions.
This research shows once again that life forms can survive in extreme conditions on Earth. This leads to the question of the possibility that bacteria-like organisms can survive, for example, in the conditions existing in the subsoil of the planet Mars, perhaps with some particular metabolism suitable for those conditions.
