Japanese biologists have discovered a community of aerobic bacteria in the cracks of volcanic rocks in the ocean at a depth of 120 meters. As reported in the journal Biology Communications, the density of unicellular organisms in crevices was extremely high — about $ 10 billion per cubic centimeter, which is comparable with the density of bacteria in the human intestine.
The upper layer of the oceanic crust consists mainly of basaltic rocks that formed during volcanic eruptions. The initial temperature of the ejected matter is very high, about 1200 degrees Celsius, but then it falls and the lava hardens, turning to stone. On cooling the basalt formed a tiny crack, not more than 1 millimeter wide, which over many millions of years are filled with clay minerals. Previous studies of rocks aged from 3.5 to 8 million years has shown that these minerals can serve as a favorable environment for anaerobic thermophiles, and aerobic mesophiles, but until now, scientists were not sure whether primitive life forms exist in the more ancient oceanic basalt.
To find the answer to this question, a group of Japanese biologists under the leadership of Yohei Suzuki (Yohey Suzuki) from the University of Tokyo in 2010 participated in ocean drilling Program (IODP) and went on a research ship in the Pacific gyre (South Pacific Gyre). With a metal shaft to a length of 5.7 kilometers and borax biologists took a small, about 6.2 cm in diameter, cores from three different areas. The first sample was raised from a depth of 51 meters below the bottom, second — from depth to 109.6 meters below the sea floor, and the third depth 121,8 meters below bottom. Depending on the location the age of the rocks was estimated at 13.5 million, 33.5 million and 104 million years.
The researchers made sure that collecting rocks was away from hydrothermal vents and channels and that bacteria get in the crack naturally, and was not caused by strong currents. In addition, to avoid contamination of the surface, the scientists sterilized the samples obtained with the help of washing with artificial sea water and quick drying. The group Suzuki coated the stones with epoxy resin to maintain the natural shape, and cut them into thin layers, which are then washed with the dye. This allowed biologists to identify the presence of microorganisms in the cracks.
X-ray analysis revealed the presence of iron-rich smectite in core samples, the age of 33.5 and 104 million years, but not in core samples, the age of 13.5 million years. In the smectite, the researchers found fluorescent signals, which indicated the presence of bacterial communities. To ensure that scientists can see living cells, and not autofluorescent materials, they have conducted additional analysis which showed that microbial cells are localized in the vicinity of the cracks.
DNA sequencing showed that the samples from different locations contain similar but not identical to each other types of bacteria. Scientists attribute this to the fact that the rocks in different places have different age that can affect their mineral composition and, as a consequence, the prevalence of different types of bacteria.
Scientists suggest that the clay mineral-filled cracks can concentrate the nutrients that bacteria use as food. According to them, this may explain why the density of bacteria in the cracks of rocks is eight orders of magnitude greater than in muddy sediments where sea water washes away the nutrients.
The group’s opinion, Suzuki, similar cracks with clay minerals can also occur on Mars. More and more studies confirm that in the past the Red planet could have liquid water on the surface and a more favorable climate. Now the Japanese biologists develop a plan to study the rocks collected from the Martian surface by Rovers, in conjunction with the Space center Lyndon B. Johnson. They propose to store the samples in a special titanium tube and explore them with the help of computer tomography and three-dimensional x-ray scan.
In 2017, “Kyuriositi” found on Mars furrows on the stone slabs, which may be mud cracks remaining after the evaporation of water. In addition, recently, the Rover found the rock, is a layer cake of sedimentary rocks, which could be formed in the presence of moving water or wind.