Fly in the primitive soup

Modeling hydrothermal sources transforms these sources of life from unlikely to practically inevitable


I arrived on the second day of creation. Laurie Barge invited me to spend one day in her life modeling lab. She is a researcher at NASA's Pasadena Laboratory, and works with her colleague, geologist Michael Russell, a member of the NASA Institute for Astrobiology. The task was to create a miniature hydrothermal source in the conditions that modeled the primitive ocean 4 billion years ago. Such sources are in the center of the scientific history of the creation of life, history is too counterintuitive to be true, and yet so logical that it simply has to be confirmed.

On the first day, Barge and his students created the oceans. They started with distilled water, and pumped nitrogen through it, replacing oxygen, which was not on the early Earth. Two early Earths in beakers placed on steel pedestals inside the hood. Then we added ferric chloride to the oceans, giving the water the color of a flat beer. I inserted a pipette tip into the bottom of each of the vessels and added sodium sulphide there, emulating hot fluid rising through the fractures of the earth's crust. Sodium reacted with chloride and created salt water, and sulfur combined with iron and formed iron sulfide precipitated as a hollow pipe. Similar tubes appeared at hydrothermal sources (GI) in the late Katharhea 4 billion years ago, and are still being formed both in bottomless seas and in the Barge laboratory.

Underwater city: this deposit in the form of a beehive formed on the side of another structure in the Lost City, a large underwater cluster of mineral tubes, some of which reach the size of buildings emitting an alkaline liquid.

The idea of ​​the origin of life in the GI is struggling with an older, well-known scientific history of the creation of life, the " primary broth ." In a letter to Joseph Hooker in 1871, Charles Darwin considered the idea that life originated "in some small, warm pond, where there were all sorts of ammonia and phosphorus salts, where there was light, heat, electricity, etc.," resulting in a "chemically formed protein compound, ready for even more complex changes." In 1924, the Russian scientist Alexander Oparin put forward a theory about the origin of life on Earth through the transformation, in the course of a gradual chemical evolution, of molecules containing carbon into “primary broth”. In 1925, he presented this idea to the English-speaking public. In 1929, the British scientist John Birdon Sanderson Haldane published his work on the birth of life with similar ideas. He wrote how life could originate in the ancient ocean, which had the consistency of "hot, diluted soup." So this name stuck.

In 1953, Stanley Miller, a graduate student who studied with Nobel Prize winner Harold Urey, successfully created a soup in a laboratory. He placed the flasks with the supposed primitive ocean and atmosphere, gave a spark using artificial lightning and collected the compounds obtained. He found many very curious, including several amino acids. Chemistry of Miller-Urey became a symbol in search of the source of life, while Miller's disciples bred and multiplied themselves. In today's study of the source of life, "soup" refers to models in which life begins on or near the ocean surface due to Miller-Urey chemistry, while lightning or other energy sources constantly unite molecules into ever-increasing states until the Darwinian evolution begins. [Plaxco, KW & Gross, M. Astrobiology: A Brief Introduction Johns Hopkins University Press, Baltimore, MD (2006)]

The soup is intuitively attractive: it is possible to derive the building blocks of life from it. But he has a fatal flaw: no matter what he produces, it is dead. Lightning can trigger biochemical reactions, but energy is quickly dissipated and the system returns to equilibrium. Primary broth requires evolution in order to climb thermodynamically, in the direction of increasing order. This is similar to gravitational hills , the descriptions of which are complete on the Internet, where the car seems to be rolling itself uphill. Amino acids and nucleotides are self-generated from heat, stones and seawater. They organized themselves into even more ordered molecules, such as enzymes and proteins. Of these, evolution built the first cells, and as a result, mahogany and roses, bees and apple trees, hyenas and people.

But the gravitational hill is a deception of perspective. The construction level would reveal deception, but you will rarely see it in these commercials with “magic” hills. The laws of physics has not been canceled. The same applies to the birth of life, as experts say on GI. It only seems that evolution is moving towards ordering; in general, it always moves downhill. GI models say that in the initial conditions the appearance of life was not akin to a miracle. It was inevitable. [Martin, W. & Russell, MJ: A hypothesis on the origins of the cells and a variety of cells. Philosophical Transactions of the Royal Society of London B: Biological Sciences 358, 59-83 (2003) / Russell, MJ & Martin, W. The rocky roots of the acetyl-CoA pathway. Trends in Biochemical Sciences 29, 358-363 (2004) / Martin, W. & Russell, MJ On the origin of biochemistry at an alkaline hydrothermal vent. Philosophical Transactions of the Royal Society of London: Biological Sciences 362, 1887-1925 (2007) / Martin, W., Baross, J., Kelley, D., & Russell, MJ Hydrothermal vents and the origin of life. Nature Reviews Microbiology 6, 805-814 (2008)]

Underwater robot examines in detail the growing structure in the Lost City

Oceanographers first discovered GI in 1977 in the Galapagos rift in the east Pacific. [Corliss, JB, et al. Submarine thermal springs on the Galápagos rift. Science 203, 1073-1083 (1979)] Then in 1979, on the crest of the East Pacific Rise at 21 degrees north latitude giant pipes were found spitting out blackish and very hot acid into cold dark depths. Quite accurately, and almost poetic, these structures were called “black smokers”. The researchers were amazed that the space near black smokers was teeming with life, ranging from fish to countless new types of microbes. In 1981, Jack Corliss, one of the oceanographers of the expedition to the Galapagos cleft, together with microbiologists John Baross and Sarah Hoffman, suggested that underwater GI "provide all the necessary conditions for creating life on Earth." No light or lightning was needed. There was no soup.

The followers of Miller went on the counter attack. The GIs were too hot to support life, Miller and his former student Jeffrey Bud wrote. Amino acids and nucleic acids, even if they appeared, would almost immediately collapse. Sahara would melt. Life could not begin in such a hostile environment. They wrote: "The sources would be an important tool for the destruction, not the synthesis of organic components in primitive oceans." [Miller, SL & Bada, JL Submarine hot springs and the origin of life. Nature 334, 609-611 (1988)]

Russell and his colleague Allan Hall, now an archaeologist at the University of Glasgow, joined the argument. They said that Miller, of course, is right - black smokers are too hot and there is too much acid in them to form life there. But next to them, they wrote, you can find mineral pipes emitting a warm alkaline liquid. This is the ideal place for the birth of life. [Russell, MJ, Hall, AJ, & Turner, D. In vitro growth of iron sulfide chimneys: possible cultures for origin ‐ of-life experiments. Terra Nova 1, 238-241 (1989)]

The stones of the hydrothermal field of the Lost City are inhabited by a wide range of deep-sea invertebrates, including a large number of corals. Crabs also consider this city their home.

And on December 4, 2000, as Russell predicted, such pipes were found, albeit accidentally. The research team led by Donna Blackman from the Scripps Institute of Oceanography, which included Deborah Kelly from the University of Washington and Jeffrey Carson from Duke University, studied the Atlantic massif, a 15-km elevation, named after the mythical city, which, according to Plato, sank in the north Atlantic after losing to Athens. Toward the end of the monthly expedition, the underwater robot deviated from the designated course, following the fish, as if it had been specially hobbled into the camera. Suddenly, the researchers saw on the screen an extensive system of pearl-white structures, some of which were the size of a building: cones, spiers, frozen windows. They could not resist because to call this place "Lost City". [Earthguide: Mid-Atlantic Ridge, journal entry, Dec. 12, 2000]

When studying it, it was found that the towers of the Lost City emit a clean, warm alkaline liquid into a slightly acidic ocean. Borders separated warm water from cold, concentrated from diluted, low pH from high. The Lost City on the early Earth would appear in a carbonated, and therefore acidic, ocean. Its porous walls of sulphides and iron oxides would make the first Lost City a weak but huge battery. [Russell, MJ, Nitschke, W., & Branscomb, E. The inevitable journey to being. Philosophical Transactions of the Royal Society of London B: Biological Sciences 368 (2013). Retrieved from doi: 10.1098 / rstb.2012.0254] Living cells are also surrounded by a membrane that separates the alkaline entrails from a slightly acidic environment. "The last universal ancestor" of life, as Barge says, "fed on the gradients of electrons and protons , like today's life." Whether it is an animal, a plant, a fungus or a bacterium, all organisms repeat the chemistry of oxidation and reduction found in warm alkaline sources. A small part of that ancient Lost City lives inside each cell.

While Barge and I watched the experiment, iron sulfide pipes began to form complex structures. The rising fluid built its exhaust pipe. A piece of crystal blocked the flow; the fluid, rising, found a new path; the structure has branched out. The result was remarkably reminiscent of a plant. The ancient alchemists created similar “chemical gardens”, and the almost forgotten nineteenth-century biologist Stephan Leduc believed that these organic forms reflect the principles of biological growth. “The life chain,” Leduk wrote, “continues uninterruptedly, from the mineral at one end to the most complex organism at the other.”

Current GI models offer an explanation for the creation of this chain. The gigantic battery of the early Lost City supports the operation of an instrument that generates complex molecules, mainly carbon, hydrogen and oxygen. Iron sulfide, like other small molecules found in sources, works like coenzymes - catalytic nano-engines, promoting reactions that lie at the very heart of the whole metabolism. Pipes, to put it simply, have a kind of metabolism, which receives energy from hydrogen, CO 2 and other molecules, and uses it to build more complex molecules, mainly from carbon, hydrogen and oxygen. The most ancient ways of metabolism in biology repeat the chemistry of the early Lost City.

Most of all our intuition is contradicted by the fact that complex structures can dissipate energy better than simple ones. [Mac McClellan, J. What is the Most Fuel Efficient Airplane? (2008)] Catalysts help you climb an energy hill so that on the other hand you can fall even lower. If we consider the entire biological evolution, then each organism represents such an energy hill. It is formed only if it is in thermodynamically favorable conditions - if we are pulling energy up a hill, we can release even more energy. Creating a lizard requires more energy than creating a certain amount of E. coli of the same mass, but it also consumes energy faster. In a world where there are lizards and bacteria, it is energetically more favorable than a world where there are only bacteria. A world where there are warm-blooded cows, chewing grass and emitting heat, methane and fertilizer - an improved version of the entropy engine; the world with tigers is even better. It is energetically beneficial to have an ecosystem: Earth with lush vegetation and teeming with life consumes more heat from the hot center of the planet and the Sun, releasing it into a cold, dark space than, say, Mars. Our biosphere is a very complex ice bubble for the sun.

A giant dispersal tool appeared with Homo sapiens. The whole history of technology is the development of increasingly efficient methods for extracting energy from
Earth and the Sun: fire, cooking, agriculture, mining, smelting, logging, steam engines. Like a stream of water running down a hill, the exact path of evolution and culture is not defined - only the general trend. Therefore, neither art, nor war, nor NASCAR, nor smartphones were inevitable - all this can be considered as the work of the engine of human entropy. In this light, our dispersion trends are not a deviation, but a thermodynamic necessity.

A miniature iron sulphide tube 5 cm tall is growing in a sea simulation in a reactive laboratory. It reproduces the larger structures associated with the GI, in which life could have originated on the ancient Earth.

If Barge and I watched the laboratory model for a long time, would it have developed a metabolic pathway through evolution? Enzymes? Genes? Maybe. The barge is taking its first steps in this direction, albeit small ones. Instead of building a pipe, it places ferrous sulfide and other minerals on a porous disk of inert material. The disk can work as a membrane between, say, positively charged and negatively charged fluid. A barge measures stress and pH differences on both sides of the membrane — then electrons and protons. These currents support chemical reactions that are fundamental to life. The next step is to make chemical reactions produce more complex molecules. “You can also do experiments,” she says, “to check for the emerging feedback of organic matter with minerals.” Simple catalysts could prefer reactions, the result of which would be more complex catalysts that could produce even more complex catalysts, and this feedback loop would eventually lead — over a long time — to proteins and DNA.

In one of my two worlds, the pipe turned out with a thin stem and a heavy thickening at the end. “This one is likely to break,” says Barge. And it breaks: a dead end of evolution. But the tube in another flask has grown a very thick base and built a conical mountain with a series of peaks that would seem majestic to a water flea. Laurie examined her and praised her.

Nathaniel Comfort - a member of the astrobiological collection of them. Baruch Blumberg at the Library of Congress / NASA and Professor of Medical History at the University. John hopkins His recent book is The Science of Human Perfection. Twitter @nccomfort.


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