Discovery of aberrant protein that kills bacterial cells could help unravel mechanism of certain antibiotics

Light microscope images of E. coli cells in transmitted light (left) and reflected light that picks up the red fluorescence of a dye staining the cells’ DNA (right). In normal cells (upper panel), the DNA is spread throughout the cells. But in cells expressing the aberrant plant protein identified in this study (bottom panel) all the DNA within each cell has collapsed into a dense mass. DNA condensation also occurs after bacteria have been treated with aminoglycoside antibiotics. Credit: Brookhaven National Laboratory

Biologists at the U.S. Department of Energy’s Brookhaven National Laboratory and their collaborators have discovered an aberrant protein that’s deadly to bacteria. In a paper just published in the journal PLOS ONE, the scientists describe how this erroneously built protein mimics the action of aminoglycosides, a class of antibiotics. The newly discovered protein could serve as a model to help scientists unravel details of those drugs’ lethal effects on bacteria—and potentially point the way to future antibiotics.

“Identifying new targets in bacteria and alternative strategies to control is going to become increasingly important,” said Brookhaven biologist Paul Freimuth, who led the research. Bacteria have been developing resistance to many commonly used drugs, and many scientists and doctors have been concerned about the potential for large-scale outbreaks triggered by these , he explained.

“What we’ve discovered is a long way from becoming a drug, but the first step is to understand the mechanism,” Freimuth said. “We’ve identified a single that mimics the effect of a complex mixture of aberrant proteins made when bacteria are treated with aminoglycosides. That gives us a way to study the mechanism that kills the bacterial . Then maybe a new family of inhibitors could be developed to do the same thing.”

Following an interesting branch

The Brookhaven scientists, who normally focus on energy-related research, weren’t thinking about human health when they began this project. They were using E. coli bacteria to study genes involved in building plant cell walls. That research could help scientists learn how to convert (biomass) into biofuels more efficiently.

But when they turned on expression of one particular plant gene, enabling the bacteria to make the protein, the cells stopped growing immediately.

“This protein had an acutely toxic effect on the cells. All the cells died within minutes of turning on expression of this gene,” Freimuth said.

Understanding the basis for this rapid inhibition of cell growth made an ideal research project for summer interns working in Freimuth’s lab.

“Interns could run experiments and see the effects within a single day,” he said. And maybe they could help figure out why a plant protein would cause such dramatic damage.

Brookhaven Lab biologist Paul Freimuth and co-author Feiyue Teng, a scientist in Brookhaven Lab’s Center for Functional Nanomaterials (CFN), at the light microscope used to image bacteria in this study. Credit: Brookhaven National Laboratory

Misread code, unfolded proteins

“That’s when it really started to get interesting,” Freimuth said.

The group discovered that the toxic factor wasn’t a plant protein at all. It was a strand of amino acids, the building blocks of proteins, that made no sense.

This nonsense strand had been churned out by mistake when the bacteria’s ribosomes (the cells’ protein-making machinery) translated the letters that make up the “out of phase.” Instead of reading the code in chunks of three letters that code for a particular amino acid, the ribosome read only the second two letters of one chunk plus the first letter of the next triplet. That resulted in putting the wrong amino acids in place.

“It would be like reading a sentence starting at the middle of each word and joining it to the first half of the next word to produce a string of gibberish,” Freimuth said.

The gibberish protein reminded Freimuth of a class of antibiotics called aminoglycosides. These antibiotics force ribosomes to make similar “phasing” mistakes and other sorts of errors when building proteins. The result: all the bacteria’s ribosomes make gibberish proteins.

“If a bacterial cell has 50,000 ribosomes, each one churning out a different aberrant protein, does the toxic effect result from one specific aberrant protein or from a combination of many? This question emerged decades ago and had never been resolved,” Freimuth said.

The new research shows that just a single aberrant protein can be sufficient for the .

That wouldn’t be too farfetched. Nonsense strands of amino acids can’t fold up properly to become fully functional. Although misfolded proteins get produced in all cells by chance errors, they usually are detected and eliminated completely by “” machinery in healthy cells. Breakdown of quality control systems could make aberrant proteins accumulate, causing disease.

Messed-up quality control

The next step was to find out if the aberrant plant protein could activate the bacterial cells’ quality control system—or somehow block that system from working.

Freimuth and his team found that the aberrant plant protein indeed activated the initial step in protein quality control, but that later stages of the process directly required for degradation of aberrant proteins were blocked. They also discovered that the difference between cell life and death was dependent on the rate at which the aberrant protein was produced.

“When cells contained many copies of the gene coding for the aberrant plant protein, the quality control machinery detected the protein but was unable to fully degrade it,” Freimuth said. “When we reduced the number of gene copies, however, the quality control machinery was able to eliminate the toxic protein and the cells survived.”

The same thing happens, he noted, in cells treated with sublethal doses of aminoglycoside antibiotics. “The quality control response was strongly activated, but the cells still were able to continue to grow,” he said.

Model for mechanism

These experiments indicated that the single aberrant plant protein killed cells by the same mechanism as the complex mixture of aberrant proteins induced by aminoglycoside antibiotics. But the precise mechanism of cell death is still a mystery.

“The good news is that now we have a single protein, with a known amino acid sequence, that we can use as a model to explore that mechanism,” Freimuth said.

Scientists know that cells treated with the antibiotics become leaky, allowing things like salts to seep in at toxic levels. One hypothesis is that the misfolded proteins might form new channels in cellular membranes, or alternatively jam open the gates of existing channels, allowing diffusion of salts and other toxic substances across the cell membrane.

“A next step would be to determine structures of our protein in complex with membrane channels, to investigate how the protein might inhibit normal channel function,” Freimuth said.

That would help advance understanding of how the aberrant proteins induced by aminoglycoside antibiotics kill —and could inform the design of new drugs to trigger the same or similar effects.

More information:
A polypeptide model for toxic aberrant proteins induced by aminoglycoside antibiotics, PLoS ONE (2022). DOI: 10.1371/journal.pone.0258794

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Hexbyte Glen Cove Scientists make rare discovery of a protein function universal to bacteria and humans

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The amino acid selenocysteine, 3D-balls model. Credit: YassineMrabet/CC BY 3.0/Wikipedia

Scientists have discovered that a human receptor protein has the ability to detect individual amino acids in exactly the same way that bacteria do.

The finding could lead to enhancements of drugs derived from the amino acid GABA, but also has evolutionary implications: It adds to the sparse evidence suggesting there are commonalities between and humans with respect to sensing the presence of essential components of life, such as oxygen and food.

Receptors on cell surfaces detect all kinds of nutrients—fats, sugars and vitamins, for example—but use different types of segments called sensors, and no common chemical detection mechanism is currently known.

In this work, scientists discovered a universal sensor present in many different that detects amino acids by precisely interacting with the two groups of atoms that are shared by all amino acids.

“For the first time, we’ve found the universal way of detecting amino acids. Nearly every organism can do it through this mechanism,” said Igor Jouline, senior author of the study and a professor of microbiology at The Ohio State University.

“In our experience, it’s very rare when we can extrapolate a very specific sensory function with such precision from bacteria to humans, because these life forms are separated by such a long evolutionary time—about 3 billion years.”

The study is published today (March 1, 2022) in Proceedings of the National Academy of Sciences.

Amino acids are the building blocks of life, assembling proteins, which perform most of the work inside cells, from the information stored in genes.

In earlier studies of a bacterium that causes human infection, Jouline’s lab and collaborators in Spain found several receptors that recognized amino acids, and identified a structural feature that all of those proteins shared. To further understand this characteristic, first author Vadim Gumerov, a research scientist in the Jouline lab, looked for other organisms that had similar receptors, scouring and comparing genomic data to zero in on that very specific structural feature, called a , that detects amino acids. Through analysis of sequence and structure information, Gumerov identified the amino acid-binding motif in human receptors.

This motif is located in an outer-facing segment of the protein that crosses a cell’s outer membrane. Combining their computations with available experimental data, the team determined that this motif exists in proteins found in organisms spanning the tree of life, with the exception of fungi and a few plant species. Further analyses showed that all of the motif-containing proteins bind amino acids—and only amino acids.

In bacteria, this sensor helps the organisms navigate toward amino acids, an important food source.

“It’s a part of a primitive nervous system for bacteria, which detects signals and helps them make decisions,” Jouline said. “There’s a spectacular parallel because in humans, this amino acid sensor is also a part of the nervous system. We identified this sensor in human calcium channels that modulate release of neurotransmitters from synapses in several neuronal tissues. Malfunctioning of these results in neuropathic pain.”

That’s where GABA comes in. Before this study, drug developers knew that medications derived from GABA (gamma-aminobutyric acid), treating neuropathic pain, fibromyalgia and seizures, relieve symptoms linked to these disorders by attaching to a protein in the human nervous system.

That protein, it turns out, is the one the research team found in humans that contains the motif enabling detection of , including GABA.

Collaborators in the United Kingdom helped confirm this finding, testing the effects of mutating the motif in experiments using a rat protein that functions in exactly the same way as the human protein. Altering the motif changed the function of the entire receptor, preventing the GABA-derived drug gabapentin from making an effective connection.

“Our work is not solving pharmacological problems, but it showed precisely where on the human protein GABA-derived drugs will bind, and also how they will bind,” Jouline said. “That’s important, because now if they want to improve it or test different versions of the drug, they know the exact chemical environment. We’re providing these two missing points—which part of the drug will bind to which amino acid of the protein, and how it’s oriented in 3D space.”

Though there may never be a definitive answer to the age-old question of what exactly bacteria and humans have in common biologically, Jouline has begun a broader search for sensors that have a role in sustaining life.

“Now we know where to look—not at whole proteins, but only at their segments that are involved in recognizing physical and chemical parameters important to all living systems,” he said.

More information:
Vadim M. Gumerov et al, Amino acid sensor conserved from bacteria to humans, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2110415119


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Hexbyte Glen Cove Breakthrough discovery in light interactions with nanoparticles paves the way for advances in optical computing

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Scattered waves from a nanoscale object encode the solution of a complex mathematical problem when interrogated by tailored input signals. Credit: Heedong Goh

Computers are an indispensable part of our daily lives, and the need for ones that can work faster, solve complex problems more efficiently, and leave smaller environmental footprints by minimizing the required energy for computation is increasingly urgent. Recent progress in photonics has shown that it’s possible to achieve more efficient computing through optical devices that use interactions between metamaterials and light waves to apply mathematical operations of interest on the input signals, and even solve complex mathematical problems. But to date, such computers have required a large footprint and precise, large-area fabrication of the components, which, because of their size, are difficult to scale into more complex networks.

A newly published paper in Physical Review Letters from researchers at the Advanced Science Research Center at the CUNY Graduate Center (CUNY ASRC) details a breakthrough discovery in nanomaterials and -wave interactions that paves the way for development of small, low-energy optical computers capable of advanced computing.

“The increasing energy demands of large data centers and inefficiencies in current computing architectures have become a real challenge for our society,” said Andrea Alù, Ph.D., the paper’s corresponding author, founding director of the CUNY ASRC’s Photonics Initiative and Einstein Professor of Physics at the Graduate Center. “Our work demonstrates that it’s possible to design a nanoscale object that can efficiently interact with light to solve complex mathematical problems with unprecedented speeds and nearly zero energy demands.”

In their study, CUNY ASRC researchers designed a nanoscale object made of silicon so that, when interrogated with carrying an arbitrary input signal, it is able to encode the corresponding solution of a complex mathematical problem into the scattered light. The solution is calculated at the speed of light, and with minimal energy consumption.”

“This finding is promising because it offers a practical pathway for creating a new generation of very energy-efficient, ultrafast, ultracompact nanoscale optical computers and other nanophotonic technologies that can be used for classical and quantum computations,” said Heedong Goh, Ph.D., the paper’s lead author and a postdoctoral research associate with Alù’s lab. “The very small size of these nanoscale optical computers is particularly appealing for scalability, because multiple nanostructures can be combined and connected together through light scattering to realize complex nanoscale computing networks.”

More information:
Heedong Goh et al, Nonlocal Scatterer for Compact Wave-Based Analog Computing, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.128.073201

Breakthrough discovery in light interactions with nanoparticles paves the way for advances in optical computing (2022, February 25)
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Hexbyte Glen Cove Nanocluster discovery will protect precious metals thumbnail

Hexbyte Glen Cove Nanocluster discovery will protect precious metals

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Credit: Pixabay/CC0 Public Domain

Scientists have created a new type of catalyst that will lead to new, sustainable ways of making and using molecules and protect the supply of precious metals.

A research team from the University of Nottingham have designed a new type of that combines features that are previously thought to be mutually exclusive and developed a process to fabricate nanoclusters of metals on a mass scale.

In their new research, published today in Nature Communications, they demonstrate that the behavior of nanoclusters of palladium do not conform to the orthodox characteristics that define catalysts as either homogeneous or heterogenous.

Traditionally, catalysts are divided into homogeneous, when catalytic centers are intimately mixed with reactant molecules, and heterogenous, where reactions take place on surface of a catalyst. Usually, chemists must make compromises when choosing one type or another, as homogeneous catalysts are more selective and active, and heterogenous catalysts are more durable and reusable. However, the nanoclusters of palladium atoms appear to defy the traditional categories, as demonstrated by studying their catalytic behavior in the reaction of cyclopropanation of styrene.

Catalysts enable nearly 80 percent of industrial processes that deliver the most vital ingredients of our economy, from materials (such as polymers) and pharmaceuticals right through to agrochemicals including fertilizers and crop protection. The high demand for catalysts means that global supplies of many useful metals, including gold, platinum and palladium, are become rapidly depleted. The challenge is to utilize each-and-every atom to its maximum potential. Exploitation of metals in the form of nanoclusters is one of the most powerful strategies for increasing the active surface area available for catalysis. Moreover, when the dimensions of nanoclusters break through the nanometre scale, the properties of the can change drastically, leading to new phenomena otherwise inaccessible at the macroscale.

The research team used analytical and imaging techniques to probe the structure, dynamics, and chemical properties of the nanoclusters, to reveal the inner workings of this unusual catalyst at the atomic level.

The team’s discovery holds the key to unlock full potential of catalysis in chemistry, leading to new ways of making and using molecules in the most atom-efficient and energy-resilient ways.

The research was led by Dr. Jesum Alves Fernandes, Propulsion Futures Beacon Nottingham Research Fellow from the School of Chemistry, he said: “We use the most direct way to make nanoclusters, by simply kicking out the atoms from bulk metal by a beam of fast ions of argon—a method called magnetron sputtering. Usually, this method is used for making coatings or films, but we tuned it to produce metal nanoclusters that can be deposited on almost any surface. Importantly, the size can be controlled precisely by experimental parameters, from single atom to a few nanometres, so that an array of uniform nanoclusters can be generated on demand within seconds.”

Dr. Andreas Weilhard, a Green Chemicals Beacon postdoc researcher in the team added: “Metal clusters surfaces produced by this method are completely ‘naked’, and thus highly active and accessible for chemical reactions leading to high catalytic activity.”

Professor Peter Licence, director of the GSK Carbon Neutral Laboratory at the University of Nottingham added: “This method of catalyst fabrication is important not only because it allows the most economical use of rare metals, but it does it the cleanest way, without any need for solvents or chemical reagents, thus generating very low levels of waste, which is an increasingly important factor for green chemical technologies.”

The University is set to embark on a large-scale project to expand on this work with research which will lead to the protection of endangered elements.

Professor Andrei Khlobystov, principal investigator of MASI, said: “Our project is set to revolutionize the ways metals are used in a broad range of technologies, and to break our dependence on critically endangered elements. Specifically, MASI will make advances in: the reduction of carbon dioxide (CO2) emissions and its valorisation into useful chemicals; the production of ‘green’ ammonia (NH3) as an alternative zero-emission fuel and a new vector for hydrogen storage; and the provision of more sustainable fuel cells and electrolyser technologies.”

Metal nanoclusters are activated for reactions with molecules, that can be driven by heat, light or electric potential, while tuneable interactions with support materials provide durability and reusability of catalysts. In particular, MASI catalysts will be applied for the activation of hard-to-crack molecules (e.g. N2, H2 and CO2) in reactions that constitute the backbone of the chemical industry, such as the Haber-Bosch process.

More information:
Blurring the boundary between homogenous and heterogeneous catalysis using palladium nanoclusters with dynamic surfaces, Nature Communications (2021). DOI: 10.1038/s41467-021-25263-6

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Hexbyte Glen Cove Exoplanet discovery tool begins its mission thumbnail

Hexbyte Glen Cove Exoplanet discovery tool begins its mission

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An image of NEID’s spectroscopic observations of the Sun. NEID’s spectral coverage extends significantly redder and bluer than the limits of human vision, enabling it to observe many critical spectral lines. NEID’s design enables high spectral resolution, large wavelength coverage, and exquisite stability. The image is inspired by the classic image of the spectrum of the sun created by N. A. Sharpe, based on data obtained at the McMath Pierce Observatory, located at Kitt Peak, where NEID is also located. Credit: Dani Zemba, Guðmundur Stefánsson, and the NEID Team

The NEID spectrometer, a new tool for the discovery of planets outside of our solar system, has now started its scientific mission at the WIYN 3.5m telescope at Kitt Peak National Observatory, Arizona.

“We are proud that NEID is available to the worldwide astronomical community for exoplanet discovery and characterization,” said Jason Wright, professor of astronomy and astrophysics at Penn State and NEID project scientist. “I can’t wait to see the results we and our colleagues around the world will produce over the next few years, from discovering new, rocky , to measuring the compositions of exoplanetary atmospheres, to measuring the shapes and orientations of planetary orbits, to characterization of the physical processes of these planets’ host stars.”

The newest and one of the most precise tools ever built to detect exoplanets, NEID will discover exoplanets by measuring the minute gravitational tug of these planets on their .

“We have reached an exciting milestone for NEID,” said Sarah Logsdon, a scientist at NSF’s NOIRLab and NEID instrument scientist. “After an extensive commissioning process, where NEID was put through its paces, NEID is embarking on its , having demonstrated that it is indeed a state-of-the-art tool for studying planets outside of our .”

The gravitational tug of orbiting planets induces a periodic velocity shift on the host star—a ‘wobble’ that can be measured by NEID. Jupiter for example induces a 13 meter per second wobble on our Sun, but the Earth induces a wobble of only about 9 centimeters per second. NEID’s single measurement precision is already better than 25 centimeters per second, enabling it to detect small wobbles with sufficient data.

“NEID represents the state of the art in Doppler spectroscopy radial velocity detection and characterization of exoplanets,” said John Callas, NN-EXPLORE project manager for NASA’s Exoplanet Exploration Program at the agency’s Jet Propulsion Laboratory (JPL). “NEID will push the existing boundaries for searching for smaller exoplanets, probing beyond the challenges that have limited past generations of RV spectrographs.”

Built as part of a joint NSF and NASA program, NEID’s mission is to enable some of the highest precision measurements currently possible, as well as to attempt to chart a path to the discovery of terrestrial planets around other stars.

“NEID has now successfully passed its final NASA review, and is in full operations as a scientific discovery tool,” said Fred Hearty, research professor at Penn State and project manager of NEID. “It was a real delight to work with this talented team, and a privilege to be a part of this group of professionals.”

The seething convection on the surface of stars, threaded by invisible lines of magnetic force and marred by ever changing active regions and “starspots” can pose a substantial challenge to NEID’s measurements. This stellar activity is one of the major impediments to enabling the detection of rocky planets like our own. For very small signals it is difficult to tell which are planets and which are just manifestations of stellar activity. However, there is one star for which we know the answer, because we know exactly how many planets orbit it—our Sun! In addition to observing stars during the night, NEID will also look at the Sun through a special smaller solar telescope that the team have developed.

“Thanks to the NEID solar telescope funded by the Heising-Simons Foundation, NEID won’t sit idle during the day,” said Eric Ford, professor of astronomy and astrophysics and director of Penn State’s Center for Exoplanets and Habitable Worlds. “Instead, it will carry out a second mission, collecting a unique dataset that will enhance the ability of machine learning algorithms to recognize the signals of low-mass planets during the nighttime.”

The solar telescope was designed, and built by Andrea Lin, a Cecilia Payne-Gaposchkin Science Achievement Graduate Fellow in astronomy and astrophysics at Penn State, with Andy Monson, NEID’s systems engineer.

“The solar telescope was fun project to work on,” said Lin. “I look forward to using NEID for my doctoral dissertation research. One of my planned projects with NEID is to look for planets around K-dwarfs. These stars line up incredibly well with NEID’s capabilities, and the radial velocity method in general, so I’m hoping to discover some small—hopefully terrestrial!—planets around nearby K-stars.”

NEID’s solar telescope marks the return of solar observations to Kitt Peak.

“The Sun points the way,” said Suvrath Mahadevan, professor of astronomy and astrophysics at Penn State and principal investigator of NEID. “For decades the iconic, and now decommissioned McMath Pierce telescope at Kitt Peak was the premier facility for studying the Sun. NEID is now the bridge that connects exoplanet science to solar observations, the Sun to the stars, and a bridge that connects Kitt Peak’s history to its present and future.”

All data from NEID’s observations of the Sun are being immediately released publicly to enable researchers to begin to address the stellar activity problem. The NASA Exoplanet Science Institute (NExScI) at Caltech / IPAC coordinates the data processing and will make the data available through the NEID science archive.

“NEID has been the incredible story of a team that has delivered, in record time of a little over four years that include seven months of stoppage for COVID and then working through the height of this pandemic, an instrument that sets a new standard and will produce breakthrough science,” said WIYN Executive Director, Jayadev Rajagopal.

More information:
The NEID blog:

Exoplanet discovery tool begins its mission (2021, July 20)
retrieved 21 July 2021

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Hexbyte Glen Cove Discovery of the oldest plant fossils on the African continent thumbnail

Hexbyte Glen Cove Discovery of the oldest plant fossils on the African continent

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A small plant whose axes divide several times before bearing oval sporangia. Credit: Univeristé de Liège

The analysis of very old plant fossils discovered in South Africa and dating from the Lower Devonian period documents the transition from barren continents to the green planet we know today. Cyrille Prestianni, a palaeobotanist at the EDDy Lab at the University of Liège (Belgium), participated in this study, the results of which have just been published in the journal Scientific Reports.

The greening of continents—or terrestrialisation—is undoubtedly one of the most important processes that our planet has undergone. For most of the Earth’s history, the continents were devoid of macroscopic life, but from the Ordovician period (480 million years ago) green algae gradually adapted to life outside the aquatic environment. The conquest of land by plants was a very long process during which plants gradually acquired the ability to stand upright, breathe in the air or disperse their spores. Plant fossils that document these key transitions are very rare. In 2015, during the expansion of the Mpofu Dam (South Africa), researchers discovered numerous in geological strata dated to the Lower Devonian (420—410 million years ago), making this a truly exceptional discovery.

Cyrille Prestianni, a palaeobotanist at the EDDy Lab (Evolution and Diversity Dynamics Lab) at the University of Liège, explains: “The discovery quickly proved to be extraordinary, since we are in the presence of the oldest fossil flora in Africa and it is very diversified and of exceptional quality. It is thanks to a collaboration between the University of Liège, the IRSNB (Royal Belgian Institute of Natural Sciences) and the New Albany Museum (South Africa) that this incredible discovery could be studied. The study, which has just been published in the journal Scientific Reports, describes this particularly diverse fossil flora with no less than 15 species analysed, three of which are new to science. This flora is also particularly interesting because of the quantity of complete specimens that have been discovered. These plants are small, with the largest specimens not exceeding 10 cm in height. They are simple plants, consisting of axes that divide two or three times and end in reproductive structures called sporangia.”

Mtshaelo kougaensis is a plant that bears complicated sporangia gathered at the end of the axes. Credit: University of Liège

The fossil flora of Mpofu suggests what the world might have been like when the largest plants were no taller than a few centimeters and almost no animals had yet been able to free themselves from the aquatic environment. It provides a better understanding of how the Earth went from a red rock devoid of life to the green planet we know today. These , simple as they are, are a crucial step in the construction of the environments that hosted the first land animals, arthropods. They form the basis of the long history of life on Earth, which continues today from dense tropical forests to the arid tundra of the north.

More information:
Robert W. Gess et al, An early Devonian flora from the Baviaanskloof Formation (Table Mountain Group) of South Africa, Scientific Reports (2021). DOI: 10.1038/s41598-021-90180-z

Discovery of the oldest plant fossils on the African continent (2021, June 9)
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Hexbyte Glen Cove Discovery of new geologic process calls for changes to plate tectonic cycle thumbnail

Hexbyte Glen Cove Discovery of new geologic process calls for changes to plate tectonic cycle

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Elements of a newly discovered process in plate tectonics include a mass (rock slab weight), a pulley (trench), a dashpot (microcontinent), and a string (oceanic plate) that connects these elements to each other. In the initial state, the microcontinent drifts towards the subduction zone (Figure a). The microcontinent then extends during its journey to the subduction trench owing to the tensional force applied by the pull of the rock slab pull across the subduction zone (Figure b). Finally, the microcontinent accretes to the overriding plate and resists subduction due to its low density, causing the down-going slab to break off (Figure c). Credit: Erkan Gün/University of Toronto

Geoscientists at the University of Toronto (U of T) and Istanbul Technical University have discovered a new process in plate tectonics which shows that tremendous damage occurs to areas of Earth’s crust long before it should be geologically altered by known plate-boundary processes, highlighting the need to amend current understandings of the planet’s tectonic cycle.

Plate tectonics, an accepted theory for over 60 years that explains the geologic processes occurring below the surface of Earth, holds that its outer shell is fragmented into continent-sized blocks of solid rock, called “plates,” that slide over Earth’s mantle, the rocky inner layer above the planet’s core. As the plates drift around and collide with each other over million-years-long periods, they produce everything from volcanoes and earthquakes to and deep ocean trenches, at the boundaries where the plates collide.

Now, using supercomputer modelling, the researchers show that the plates on which Earth’s oceans sit are being torn apart by massive tectonic forces even as they drift about the globe. The findings are reported in a study published this week in Nature Geoscience.

The thinking up to now focused only on the geological deformation of these drifting plates at their boundaries after they had reached a , such as the Marianas Trench in the Pacific Ocean where the massive Pacific plate dives beneath the smaller Philippine plate and is recycled into Earth’s mantle.

The new research shows much earlier damage to the drifting plate further away from the boundaries of two colliding plates, focused around zones of microcontinents—continental crustal fragments that have broken off from main continental masses to form distinct islands often several hundred kilometers from their place of origin.

“Our work discovers that a completely different part of the plate is being pulled apart because of the subduction process, and at a remarkably early phase of the tectonic cycle,” said Erkan Gün, a Ph.D. candidate in the Department of Earth Sciences in the Faculty of Arts & Science at U of T and lead author of the study.

Elements of a newly discovered process in plate tectonics include a mass (rock slab weight), a pulley (trench), a dashpot (microcontinent), and a string (oceanic plate) that connects these elements to each other.In the initial state, the microcontinent drifts towards the subduction zone (Figure a).The microcontinent then extends during its journey to the subduction trench owing to the tensional force applied by the pull of the rock slab pull across the subduction zone (Figure b).Finally, the microcontinent accretes to the overriding plate and resists subduction due to its low density, causing the down-going slab to break off. Credit: Erkan Gün/University of Toronto

The researchers term the mechanism a “subduction pulley” where the weight of the subducting portion that dives beneath another tectonic plate, pulls on the drifting ocean plate and tears apart the weak microcontinent sections in an early phase of potentially significant damage.

“The damage occurs long before the microcontinent fragment reaches its fate to be consumed in a subduction zone at the boundaries of the colliding plates,” said Russell Pysklywec, professor and chair of the Department of Earth Sciences at U of T, and a coauthor of the study. He says another way to look at it is to think of the drifting ocean plate as an airport baggage conveyor, and the microcontinents are like pieces of luggage travelling on the conveyor.

“The conveyor system itself is actually tearing apart the luggage as it travels around the carousel, before the luggage even reaches its owner.”

The researchers arrived at the results following a mysterious observation of major extension of rocks in alpine regions in Italy and Turkey. These observations suggested that the tectonic plates that brought the rocks to their current location were already highly damaged prior to the collisional and mountain-building events that normally cause deformation.

“We devised and conducted computational Earth models to investigate a process to account for the observations,” said Gün. “It turned out that the temperature and pressure rock histories that we measured with the virtual Earth models match closely with the enigmatic rock evolution observed in Italy and Turkey.”

According to the researchers, the findings refine some of the fundamental aspects of and call for a revised understanding of this fundamental theory in geoscience.

“Normally we assume—and teach—that the ocean plate conveyor is too strong to be damaged as it drifts around the globe, but we prove otherwise,” said Pysklywec.

More information:
Erkan Gün et al, Pre-collisional extension of microcontinental terranes by a subduction pulley, Nature Geoscience (2021). DOI: 10.1038/s41561-021-00746-9

Discovery of new geologic process calls for changes to plate tectonic cycle (2021, May 11)
retrieved 12 May 2021

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