original version of this story Appeared in Quanta Magazine.
Scientists have discovered that in the soil and rocks beneath our feet, vast biosphere The total volume of the Earth is almost twice the volume of the entire world’s oceans. Little is known about these subterranean organisms, but they make up a large portion of Earth’s microbial population, and their diversity may exceed that of surface life. Their existence is a great mystery. Researchers have long assumed that many of these subterranean regions are oxygen-starved, dead zones, inhabited only by primitive microorganisms that maintain vitality. Metabolism spikes and scrape away any traces of nutrients. It was thought that once those resources were depleted, the underground environment would become deeper and life would be lost.
in new research Published in June nature communications, researchers have presented evidence that challenges those assumptions. Researchers have discovered that a groundwater reservoir 200 meters underground in a fossil fuel field in Alberta, Canada, is rich in microorganisms that can unexpectedly produce large amounts of oxygen even in the absence of light. Microbes produce and emit large amounts of what researchers call “dark oxygen,” so it’s like discovering “the scale of oxygen provided by photosynthesis in the Amazon rainforest.” Karen LloydHe is an underground microbiologist at the University of Tennessee, but was not involved in the study. The amount of gas that diffuses from the cells is so large that it is thought to create favorable conditions for oxygen-dependent life in the surrounding groundwater and geological formations.
“This is groundbreaking research,” he said. barbara sherwood lorer, a geochemist at the University of Toronto, was not involved in the study. Although past studies have often considered mechanisms for producing hydrogen and other molecules important to subterranean organisms, the production of oxygen-containing molecules has been difficult since such molecules are rapidly consumed in the subsurface environment. It has been largely overlooked. Until now, “no study has put everything together like this one,” she says.
A new study examines the deep aquifers in Canada’s Alberta province, a province so rich in underground tar, oil sands and hydrocarbons that it has been nicknamed the “Texas of Canada.” Large-scale livestock and agricultural industries rely heavily on groundwater, so the state government actively monitors water acidity and chemical composition. However, no one had systematically studied the microbiology of groundwater.
for Emil RuffWhen she began her postdoctoral research in microbiology at the University of Calgary in 2015, conducting such a study seemed like a “low-hanging fruit.” Little did he know that this seemingly simple research would burden him for the next six years.
crowded depths
After collecting groundwater from 95 wells across Alberta, Ruff and his colleagues began doing basic microscopy. Microbial cells in groundwater samples were stained with nucleic acid dyes and cell numbers were counted using fluorescence microscopy. By radiometrically dating organic matter in the samples and determining the depth at which they were taken, the researchers were able to determine the age of the groundwater aquifer they were harvesting from.
The pattern of numbers puzzled them. For example, when studying sediments beneath the ocean floor, scientists typically find that the number of microbial cells decreases with depth. Older, deeper samples cannot support as much life because they are more cut off from nutrients made by photosynthetic plants. and algae near the surface. But to Ruff’s team’s surprise, older, deeper groundwater had more cells than freshwater.
The researchers then used molecular tools to begin identifying the microorganisms in the samples, finding telltale marker genes. Many are methanogenic archaea, simple single-celled microorganisms that produce methane by consuming hydrogen and carbon oozing from rocks and decaying organic matter. There were also many bacteria that fed on methane and minerals in the water.
