Little West

Japanese scientists have discovered dense clusters of bacteria inside rocky crevices in the deep ocean. This discovery provides evidence that other environments such as the Mars planet can also be a haven for microscopic life.

The discovery of this microscopic life in these harsh conditions was a surprise to the researchers, so they expect to find a similar form of microscopic life in Mars, says Yohei Suzuki of the University of Tokyo, the main author of the study published on the "Nature" magazine on the second of April. .

Mud substance of life
The researchers say that the volcanic rock crevices studied in the depths of the oceans are home to groups of bacteria the density of which compares with those in the human intestine estimated at about ten billion bacterial cells per cubic centimeter.

It is a very high density compared to its average density in other places, like other mud sediments on the sea floor that do not exceed one hundred cells per cubic centimeter.

When volcanoes beneath the surface of the sea explode, they release hot lava with a temperature of about 1,200 ° C. Then, when cooled, they turn into rocks punctuated by narrow cracks, the width of which may not exceed one millimeter.

Over millions of years, these cracks are filled with clay materials and somehow, bacteria find their way to these cracks and multiply.

"These cracks are a very friendly place to live," says Suzuki. "Clay is a magical substance on Earth. The more you find clay, the more you will find microbes living in it."

Slices of bacteria-bearing rock samples (University of Tokyo)

Researchers have discovered these bacteria in rock samples since 2010 in three locations in the Pacific between Tahiti and New Zealand, and classified them as aerobic bacteria, which means they depend on oxygen and organic nutrients to produce energy just like human cells.

Creative way
Scientists have estimated the age of rock samples to be between 13.5 million and 104 million years. And they noticed that the three sites from which they were taken were far from any thermal water vents or water currents under the seabed, so they believed that bacteria independently reached the cracks and the currents did not carry them there.

The team used an innovative method to find bacteria in rock samples. Instead of removing the outer layer of the rocks and grinding their internal content into powder as applied in traditional methods, Suzuki and his team used a method similar to that of pathologists preparing very thin slices of body tissue samples to diagnose Disease, by painting the rocks with a special coating to support their natural shape so that they do not collapse when they cut them into thin slices.

These thin sheets of hard rock were then washed with a DNA stain stain before being placed under a microscope. The surprise was under the electron microscope. The bacteria appeared in the form of glowing green balls and tightly packed in glowing tunnels in an orange color, surrounded by black rocks.

Sectional images of rock samples containing bacteria, basalt rocks in gray and clay materials in orange and bacteria in green (University of Tokyo)

Favorable environment
This orange glow comes from clay mineral deposits called the "magical substance" that give bacteria an attractive place to live. Full genomic DNA analysis identified the different types of bacteria that lived in the cracks.

The researchers found that the types of bacteria extracted from the samples were similar, but not identical, because of the difference in age of the rocks in the three sites, which affects minerals that require a long time to accumulate in the cracks.

Suzuki and colleagues suggest that clay-filled cracks focus the nutrients that bacteria use as fuel. This explains why the density of bacteria in rock fissures is greater than that of bacteria that live freely in clay deposits where seawater weakens nutrients.

From the ocean to Mars
The authors of the study consider that the clay minerals that fill cracks in the deep ocean rocks may be similar to the minerals that may now be in the rocks on the surface of Mars.

They also see that this discovery may enhance the chances of finding a form of life on it. They have already started, in cooperation with NASA, in designing a plan to examine the rocks collected from the surface of Mars.