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The life would not exist without energy: organisms need to breathe, reproduce, find food… But there are beings that live in a kind of torpor, as in a hibernation is continuous, that are also technically alive though seem otherwise. What, then, is where is the limit of life ? What is the minimum energy needed by the living beings to be seen, precisely, living?

that is the question that you have wanted to answer a team from the Research Centre for Geosciences, Germany (GFZ) and the Queen Mary University (London). Led by James Bradley , of the GFZ, have come to a startling conclusion: there are microbes in the seafloor to survive with a lot less energy than you thought until now. The study has just been published in the journal “Science Advances”.

“they are Not dead”

“When we think about the nature of life on Earth, we see plants, animals, microscopic algae and bacteria, constantly active, grow and reproduce. But here we show that any a biosphere of micro-organisms , as many cells as are found in all soils, or oceans of Earth, has barely enough energy to survive. Many of them simply exist in a state mostly idle. Do not grow, do not divide and do not develop more. These microbes are not dead, but use much less energy than is thought to continue to live,” explains Bradley.

to reach this conclusion, the team conducted a global map comparing the availability of energy at the seabed with the data of life in the past 2.6 million years in the history of the Earth, thanks to the drilling cores collected throughout the world (samples excavated from the subsoil that give data about the life, the geology of the area and other information of the site’s past). Specifically, we divided the seabed in thousands of individual cells that are then superimposed to an overall image of the biosphere of the subsoil beneath the seabed, including ways of life and key biogeochemical processes.

Photograph taken of ALVIN, a submersible, manned research in the depths of the ocean, which takes cores of sediment in the bottom of the ocean, the Outcrop of Gold in 2014 – Geoff Wheat, NSF OCE 1130146, and the National Deep Submergence FacilityUn map of the ocean floor

By combining data on the distribution and the amounts of carbon and microbial life contained in the biosphere deep in the Earth with the rate of biological and chemical reactions, the researchers were able to determine the consumption of “ power ” of individual microbial cells. In other words, the rate of energy used by life to stay active and perform essential functions like growth and repair and replacement of biomolecules. Thus it is proved that the life was of much less energy of thought through the time to, at least, survive .

“With so little energy available, it is unlikely that organisms can reproduce or divide, but that use this small amount of energy to “keep” , replacing or repairing its damaged parts. Therefore, it is likely that many of the microbes that are found at great depths below the seabed are remnants of populations that lived in shallow coastal areas for thousands or millions of years”, they say in the research. Populations of the prehistoric with latent life.

Methane as a source of energy

in Addition to these maps revealed another surprise: although the oxygen is the source of energy most important to the most common life of the Earth, is found only in the 2.7% of the oceanic sediments . That is to say, that on the seafloor, oxygen is not the main “engine” of the beings that dwell in the depths. There, the microbes produce methane (in the 64.3% of the sediment ) and oxidized sulphate ( 33% of the sediment ) as sources of energy.

methane is a powerful greenhouse gas, and the fact that these microorganisms, in spite of having a latent life, using it as a source of energy, it is very important to regulate the cycle of carbon and nutrients in the Soil. Despite the fact that they require very little “food” for methane to be so many and live so long, their impact on the system is evident.

Life on other worlds

on the other hand, the carry beyond the limits of habitability, may this research serve as support for other studies that explain where, when and how life originated on Earth or even where it could be given in other places in the Solar System.

“The results of the research challenge not only the nature and the limits of life on Earth, but also in other parts of the universe -apostille Bradley-. If there is life on Mars, for example, or in Europe-a moon of Saturn-is more likely to seek refuge under the ground. If the microbes require only a few zeptovatios able to survive, there could be remains of life under the icy surfaces of these worlds. The organisms might have lain dormant for a long time, but it would still be technically ‘alive'”. Even in slumber, the finding would be revolutionary.

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