New Extremophiles: crustal grit (Introduction)

by David Turell , Wednesday, July 12, 2023, 19:48 (500 days ago) @ David Turell

Amassing how many organisms it hides:

https://www.quantamagazine.org/in-a-fierce-desert-microbe-crusts-show-how-life-tamed-th...

"...Patrick Jung couldn’t get the checkerboard out of his head. Having spotted what looked like lichens on some of the dark pebbles, Jung suspected that something more might inhabit them. Eventually, he picked up a rock, dribbled some water on it from a bottle, and peered at it through his handheld magnifying lens. The face of the black stone erupted with green. The rubble had come alive.

"Jung whipped a photosynthesis monitor out of his pack. One tap of its fluorescent blue sensor confirmed that something within the rocks was converting carbon dioxide to oxygen. After Jung’s colleagues, Büdel included, replicated the experiment, they all danced with excitement under the desert sun...All around them, the dark patches repeated across the landscape, each one filled with its own microscopic universe.

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"...dedicated to the study of the unusual community of microbes, now known as grit crust. His team has worked to understand the extreme adaptations that have allowed these microorganisms to inhabit a land so infamously hostile, where they are refreshed only occasionally by sips of fog. The answers they have uncovered offer clues about how life may have first found a grip on our planet’s surface billions of years ago.

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"The discovery of the grit crust transformed the desert for Gutiérrez Alvarado, who has patrolled it every day for the last decade. “It’s not only rocks, not only empty space,” he said, peering out over the patches of pebbles. “Everything is breathing now.”

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"Driving through Pan de Azúcar with Gutiérrez Alvarado is like riding in a geological time machine. Ancient volcanic caverns from one epoch fade to rolling hills of eroded sand from another, between the hills peeks an outcropping of the mother bedrock, a heap of quartz spiced with different minerals. At its feet lie its progeny, smaller chunks that have broken off over millions of years. Below them sits a parade of progressively smaller rocks, all the way down to the earring-size grains that first captivated Jung. The pebbles, which litter the desert floor, are known locally as “maicillo” and in English as “grit.” The substrate is amply porous, offering plenty of cracks and corners for microbes to nuzzle into. Wedged into the crevices of each grade of rock are tiny thickets of green and black life.

"...From DNA samples, he deduced that the grit crust is composed of several hundred species of cyanobacteria, green algae and fungi — including several previously unknown lichen combinations...his colleagues sliced the stones thin for imaging. The photos showed how individual fungal hyphae had drilled deep into the rocks, carving out networks of branching canals.

"At first glance, the grit crust could seem like a routine example of what researchers call a biological soil crust, or “biocrust” — a community of coexisting bacteria, fungi, algae and other microorganisms that caps the soil in coherent sheets. Around 12% of Earth’s land is covered by biocrusts. Ecologists often refer to these colonies as the planet’s “living skin.”

"Over the last century, scientists have identified biocrusts around the globe and worked to understand their role in shaping ecosystems. They’ve learned that the crusts anchor soil grains in place and provide the organisms growing in that soil with essential nutrients such as carbon, nitrogen and phosphorus. In 2012, Büdel and colleagues estimated that biocrusts soak up and recycle around 7% of all the carbon and nearly half of all the nitrogen that is chemically “fixed” by terrestrial vegetation. The role of the biocrusts in procuring digestible nitrogen is particularly critical in arid deserts: Elsewhere, lightning can often convert atmospheric nitrogen to nitrates, but in the deserts, electrical storms are rare.

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“...van den Brink marveled. “How does anything survive here?” An enormous article filled with much more information about how these plants survive.

"The answer is the distinctive thick fog that rolls up the Chilean coastline, a weather phenomenon known locally as the camanchaca. With so little rainfall, all life in Pan de Azúcar ultimately depends on whatever moisture the fog carries. The guanaco, for example, relies on sips of water that is trapped by mosses clinging to cacti, which grow in soil fertilized by grit crust.

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“'The grit crust is setting a new threshold for conditions that make life possible,” Jung said.

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"While all biocrusts perform some degree of weathering, the larger grains of the grit crust are especially suited for it. The process reveals the full potential of microbes to impact their environment. A microbial skin can glue together pebbles, break them down into soil and fertilize that soil with essential nutrients. In effect, the crust can “terraform” the desert.

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"Gregory Retallack, an emeritus professor, believes he has found evidence for communities resembling biocrusts in fossilized soils (or “paleosols”) as far back as 3.7 billion years ago — challenging the common assumption that life originated in the sea. “The evidence from paleosols is pretty clear that there were all sorts of things on land, even very early on,” he said. “You can see these microbial crust fabrics just with the naked eye.'”

Comment: this establishes that these were the first land plants