To kill drug-resistant bacteria, “last-resort” antibiotics borrow a tactic from Medusa’s playbook: petrification.
New high-resolution microscope images show that a class of antibiotics called polymyxins crystallize the cell membranes of bacteria. The honeycomb-shaped crystals that form turn the microbes’ usually supple skins of fat molecules into thin brittle sheets , researchers report October 21 in Nature Communications . When the petrified membranes break, the bacteria die.
The finding was a total surprise, says Sebastian Hiller, a structural biologist at the University of Basel in Switzerland.
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Hiller, biophysicist Selen Manioğlu and their colleagues had been using the antibiotics as a control for a different experiment. When the researchers turned on their microscopes, “we saw these waffles,” Hiller says. “I immediately recognized, wow, this must be something special.”
Polymyxin antibiotics like colistin were discovered in the 1940s and are now used as a powerful last-ditch defense against bacteria that have evolved resistance to most other drugs. Researchers already knew that polymyxins somehow interfere with bacterial cell membranes. But nobody had imagined a scenario like the “waffles” the team discovered.
In the new study, Hiller and colleagues exposed bits of cell membrane from Escherichia coli to varying concentrations of colistin. Imaging with atomic force microscopy revealed that crystals formed at the minimum concentrations required to kill the bacteria. Colistin-resistant strains exposed to the drug didn’t form crystals.
The results indicate that polymyxins work by arranging the cell membrane into a crystalline structure that leaves it brittle and vulnerable. “That’s something that has not even remotely been hypothesized so far,” says Markus Weingarth, a biochemist at Utrecht University in the Netherlands who was not involved in the work. “It’s a very important study. I’d even say it’s a breakthrough.”
How exactly polymyxins crystallize cell membranes remains unclear. That’s a problem because some bacteria have developed resistance to polymyxins and are becoming more widespread ( SN: 5/27/16 ; SN: 10/30/90 ) . Without more studies like this one to help reveal how the drugs work, scientists can’t effectively modify the antibiotics to make them more effective, Weingarth says.
Hiller hopes that this first glimpse of polymyxins’ petrifying powers will help scientists combat resistance to the antibiotics.
“Understanding these concepts will definitely bring a lot of ideas — and the potential to make new drugs,” Hiller says.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
Carved into this ivory comb, dating to 1,700 B.C., is a sentence warding off lice that’s written in the early language of the ancient Canaanites, a new study finds.
Engraved into the side of a nearly 4,000-year-old ivory comb is a simple wish: Get these lice out of my hair.
This faint inscription, written in the early language of the ancient Canaanites, represents the earliest known instance of a complete sentence written using a phonetic alphabet, says archaeologist Yosef Garfinkel of the Hebrew University of Jerusalem.
The writing system of the Canaanites , who lived in a region in the eastern Mediterranean called the Levant until around 2,000 years ago, later served as a major basis for many modern alphabets ( SN: 7/27/17 ). That makes the comb “the most important object I’ve ever found during an excavation,” says Garfinkel. The research was published November 9 in the Jerusalem Journal of Archaeology .
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The Canaanites were a cultural group that traded widely across the Mediterranean. Few of their written records have survived, so most of what researchers know about them come from other documents, such as the Old Testament.
The comb was the unearthed in 2016 among the ruins of the ancient city of Lachish in present-day Israel. Years later, when the comb was sent to a lab to search for traces of lice, someone noticed faint symbols etched on the side. A closer look revealed that the symbols spelled out the sentence, “May this tusk root out the lice of the hair and the beard,” Garfinkel and colleagues report November 9 in the Jerusalem Journal of Archaeology .
The discovery may offer a glimpse into the life of one of Lachish’s wealthy denizens. The fact that the sentence refers to a beard suggests it belonged to an elite man, Garfinkel says, since elephant ivory was an expensive good that had to be imported from Egypt.
The plea against lice is “so human,” says Garfinkel, who notes that other writings from the time tend to center around royal accomplishments or religion. It also appears that the comb was able to fulfill its purpose, at least somewhat. Between the teeth, the researchers found the ancient remains of a louse.
Freda Kreier was a fall 2021 intern at Science News . She holds a bachelor’s degree in molecular biology from Colorado College and a master’s in science communication from the University of California, Santa Cruz.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
Ecuador’s iconic Jambato harlequin frog (one seen here) was thought to have gone extinct in the late 1980s. In 2016, it became one of many members of its genus to be rediscovered since 2000.
Across Central and South America, one group of bejeweled frogs is making a comeback.
Harlequin frogs — a genus with over 100 brightly colored species — were one of the groups of amphibians hit hardest by a skin-eating chytrid fungus that rapidly spread around the globe in the 1980s ( SN: 3/28/19 ). The group is so susceptible to the disease that with the added pressures of climate change and habitat loss, around 70 percent of known harlequin frog species are now listed as extinct or critically engendered.
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But in recent years, roughly one-third of harlequin frogs presumed to have gone extinct since the 1950s have been rediscovered, researchers report in the December Biological Conservation .
The news is a rare “glimmer of hope” in an otherwise bleak time for amphibians around the globe, says Kyle Jaynes, a conservation biologist at Michigan State University in Hickory Corners.
For Jaynes, the path to uncovering how many harlequin frogs have returned from the brink of extinction started when he heard about the Jambato harlequin frog ( Atelopus ignescens ). This black and orange frog was once so widespread in the Ecuadorian Andes that its common name comes from the word ” jampatu ,” which means “frog” in Kichwa, the Indigenous language of the area.
Then came the fungus. From 1988 to 1989, the frogs “just completely disappeared,” Jaynes says. For years, people searched for traces of the frogs. Scientists ran extensive surveys, and pastors offered rewards to their congregants for anyone that could find one.
Then in 2016, a boy discovered a small population of Jambato frogs in a mountain valley in Ecuador. For a species that had been missing for decades, “it seemed like a miracle,” says Luis Coloma, a researcher and conservationist at the Centro Jambatu de Investigación y Conservación de Anfibios in Quito, Ecuador.
Coloma runs a breeding program for Jambato and other Ecuadorian frogs threatened with extinction. In 2019, Jaynes was part of a group of researchers visiting Coloma’s lab to see if they could work out how these frogs had cheated death. After the Jambato frogs returned to the scene, the team started hearing about other missing harlequin species being spotted for the first time in years.
Those stories led Jaynes, Coloma and their colleagues to comb through reports to see just how many harlequin frogs had reappeared. Of the more than 80 species to have gone missing since 1950, as many as 32 species were spotted in the last two decades — a much higher number than the team had expected.
“I think we were all shocked,” Jaynes says.
The news comes with caveats. For one thing, it seems like most species avoided disappearing by a hair, and their numbers are still dangerously low. So extinction is still very much on the table. “We’ve got a second chance here,” Jaynes says. “But there is still a lot we have to do to conserve these species.”
Ensuring the continuation of the rediscovered species will depend in part on understanding how they’ve managed to survive so far. Some scientists have speculated that amphibians at higher elevations might be more susceptible to the fungus since it prefers lower temperatures.
But a cursory analysis by Jaynes and colleagues revealed that harlequin frogs are being rediscovered at all elevations across their range, indicating that something else may be at play. Jaynes suspects that there is a biological basis for which harlequin frogs live, such as having developed resistance to the fungus ( SN: 3/29/18 ).
Studies like this one can serve as a “launching pad” for understanding how amphibians might survive the dual threats of disease and climate change, says Valerie McKenzie, a disease ecologist at the University of Colorado Boulder who was not involved with the study.
In the meantime, the fact that people are starting to notice the reemergence of species that were once thought to be gone forever “gives me a lot of hope that other species that are harder to observe — because they’re nocturnal or live high in the canopy — are also recovering,” she says. “It motivates me to think we should go look for them.”
Freda Kreier was a fall 2021 intern at Science News . She holds a bachelor’s degree in molecular biology from Colorado College and a master’s in science communication from the University of California, Santa Cruz.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
The Nioghalvfjerdsfjord glacier (pictured) is one outlet of the roughly 600-kilometer-long Northeast Greenland Ice Stream, which drains ice from the country’s massive ice sheet into the sea.
Sea level rise may proceed faster than expected in the coming decades, as a gargantuan flow of ice slithering out of Greenland’s remote interior both picks up speed and shrinks.
By the end of the century, the ice stream’s deterioration could contribute to nearly 16 millimeters of global sea level rise — more than six times the amount scientists had previously estimated, researchers report November 9 in Nature .
The finding suggests that inland portions of large ice flows elsewhere could also be withering and accelerating due to human-caused climate change , and that past research has probably underestimated the rates at which the ice will contribute to sea level rise ( SN: 3/10/22 ).
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“It’s not something that we expected,” says Shfaqat Abbas Khan, a glaciologist at the Technical University of Denmark in Kongens Lyngby. “Greenland and Antarctica’s contributions to sea level rise in the next 80 years will be significantly larger than we have predicted until now.”
In the new study, Khan and colleagues focused on the Northeast Greenland Ice Stream, a titanic conveyor belt of solid ice that crawls about 600 kilometers out of the landmass’s hinterland and into the sea. It drains about 12 percent of the country’s entire ice sheet and contains enough water to raise global sea level more than a meter. Near the coast, the ice stream splits into two glaciers, Nioghalvfjerdsfjord and Zachariae Isstrøm.
While frozen, these glaciers keep the ice behind them from rushing into the sea , much like dams hold back water in a river ( SN: 6/17/21 ). When the ice shelf of Zachariae Isstrøm collapsed about a decade ago, scientists found that the flow of ice behind the glacier started accelerating . But whether those changes penetrated deep into Greenland’s interior remained largely unresolved.
“We’ve mostly concerned ourselves with the margins,” says atmosphere-cryosphere scientist Jenny Turton of the nonprofit Arctic Frontiers in Tromsø, Norway, who was not involved in the new study. That’s where the most dramatic changes with the greatest impacts on sea level rise have been observed, she says ( SN: 4/30/22, SN: 5/16/13 ).
Keen to measure small rates of movement in the ice stream far inland, Khan and his colleagues used GPS, which in the past has exposed the tortuous creeping of tectonic plates ( SN: 1/13/21 ). The team analyzed GPS data from three stations along the ice stream’s main trunk, all located between 90 and 190 kilometers inland.
The data showed that the ice stream had accelerated at all three points from 2016 to 2019. In that time frame, the ice speed at the station farthest inland increased from about 344 meters per year to surpassing 351 meters per year.
The researchers then compared the GPS measurements with data collected by polar-orbiting satellites and aircraft surveys. The aerial data agreed with the GPS analysis, revealing that the ice stream was accelerating as far as 200 kilometers upstream. What’s more, shrinking — or thinning — of the ice stream that started in 2011 at Zachariae Isstrøm had propagated more than 250 kilometers upstream by 2021.
“This is showing that glaciers are responding along their length faster than we had thought previously,” says Leigh Stearns, a glaciologist from the University of Kansas in Lawrence, who was not involved in the study.
Khan and his colleagues then used the data to tune computer simulations that forecast the ice stream’s impact on sea level rise. The researchers predict that by 2100, the ice stream will have singlehandedly contributed between about 14 to 16 millimeters of global sea level rise — as much as Greenland’s entire ice sheet has in the last 50 years.
The findings suggest that past research has probably underestimated rates of sea level rise due to the ice stream, Stearns and Turton say. Similarly, upstream thinning and acceleration in other large ice flows, such as those associated with Antarctica’s shrinking Pine Island and Thwaites glaciers , might also cause sea levels to rise faster than expected, Turton says ( SN: 6/9/22, SN: 12/13/21 ).
Khan and his colleagues plan to investigate inland sections of other large ice flows in Greenland and Antarctica, with the hopes of improving forecasts of sea level rise ( SN: 1/7/20 ).
Such forecasts are crucial for adapting to climate change, Stearns says. “They’re helping us better understand the processes so that we can inform the people who need to know that information.”
Nikk Ogasa is a staff writer who focuses on the physical sciences for Science News . He has a master’s degree in geology from McGill University, and a master’s degree in science communication from the University of California, Santa Cruz.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
In July 2017, after weeks of anticipation, a massive iceberg about the size of Delaware split from the Antarctic Peninsula ( SN: 7/12/17 ). Satellite images show that the orphaned iceberg, known as A68, ultimately disintegrated in the Southern Ocean. Now, researchers say they have pieced together the powerful forces that led to that final breakup.
Polar scientist Alex Huth of Princeton University and colleagues combined observations of the iceberg’s drift with simulations of ocean currents and wind stress. Iceberg A68a, the largest remaining chunk of the original berg, was caught in a tug-of-war of ocean currents, and the strain of those opposing forces probably pulled the iceberg apart , the team reports October 19 in Science Advances .
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After A68’s separation from the Larsen C ice shelf, researchers had questions — such as what creatures live on the seafloor in the ice’s dark shadow ( SN: 2/8/19 ). As for the iceberg itself, it took a while to get moving , lingering in the neighborhood for about a year ( SN: 7/23/18 ). By December 2020, satellite images show, the berg had clearly seen some action and was just two-thirds of its original size.
The new simulations suggest how A68a probably met its fate. On December 20, 2020, the long, slender “finger” at one end of the iceberg drifted into a strong, fast-moving current. The rest of the ice remained outside the current. The tension rifted the berg, and the finger sheared off and broke apart within a few days.
Shear stress is a previously unknown mechanism for large iceberg breakup, and isn’t represented in climate simulations, the team says. In the Southern Ocean, the melting of massive bergs can be a large source of cold freshwater to the ocean surface. That, in turn, can have a big impact on ocean circulation and the global climate.
Carolyn Gramling is the earth & climate writer. She has bachelor’s degrees in geology and European history and a Ph.D. in marine geochemistry from MIT and the Woods Hole Oceanographic Institution.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
What constitutes a suburb, or the middle class? Social scientists often define these and other terms in markedly different ways, leading to a maze of confusing or contradictory findings.
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U.S. millennials are rejecting suburbia and moving back to the city. That was a prevailing idea in 2019, when I started as the social sciences reporter at Science News . But when I began digging into a possible story on the phenomenon, I encountered an incoherent mess. Some research showed that suburbs were growing, others that suburbs were shrinking and yet others showed growth in both suburbs and cities.
Unable to make sense of that maze of findings, I shelved the story idea. Then, several months later, I stumbled across a Harvard University white paper explaining that disagreement in the field stems from competing definitions of what distinguishes a city from a suburb. Some researchers define the suburbs as areas falling outside census-designated cities. Others look only for markers of suburbanism, such as a wealth of single-family houses and car-based commutes, the researchers wrote.
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I have encountered this type of fuzziness around definitions of all sorts of terms and concepts in the years I’ve covered the social sciences. Sometimes researchers simply assume that their definition of a key concept is the definition. Or they nod briefly at other definitions, and then go forth with whichever one they choose, without much explanation why. Other times, researchers in one subfield choose one definition, and researchers in another subfield choose a different one — each without ever knowing of the other’s existence. It’s enough to drive any reporter to tear their hair out.
“If you look … you will find this morass of definitions and measurements” in the social sciences, says quantitative psychologist Jessica Flake of McGill University in Montreal. My experience was a common one, she assured me.
Definitional morasses exist in other scientific fields too. Biologists frequently disagree about how best to define the word “species” ( SN: 11/1/17 ). Virologists squabble over what counts as “alive” when it comes to viruses ( SN: 11/1/21 ). And not all astronomers are happy with the decision to define the word “planet” in a way that left Pluto out in the cold as a mere dwarf planet ( SN: 8/24/21 ).
But the social sciences have some special challenges, Flake says. The field is a youngster compared with a discipline like astronomy, so has had less time to sort out its definitions. And social science concepts are often inherently subjective. Describing abstract ideas like motivation or feelings can be squishier than describing, say, a meteorite.
It’s tempting to assume, as I did until I began researching this column, that a single, imperfect definition for individual concepts is preferable to this definitional cacophony. And some researchers encourage this approach. “While no suburban definition will be perfect, standardization would increase understanding of how suburban studies relate to each other,” the Harvard researchers wrote in that suburbia paper.
But a recent study taking aim at how we define the middle class showed me how alternative definitions can lead to a shift in perspective.
While most researchers use income as a proxy for class, these researchers used people’s buying patterns. That revealed that a fraction of people who appear middle class by income struggle to pay for basic necessities, such as housing, child care and groceries, the team reported in July in Social Indicators Research . That is, they live as if they are working class .
What’s more, that vulnerable group skews Black and Hispanic, a disparity that arises, in part, because these families of color often lack the generational wealth of white families, says Melissa Haller, a geographer at Binghamton University in New York. So when calamity strikes, families without that financial cushion can struggle to recover. Yet a government or nonprofit organization looking to direct aid toward the neediest families, and relying solely on income-based metrics, would overlook this vulnerable group.
“Depending on what definition you start with, you will see different facts,” says Anna Alexandrova, a philosopher of science at the University of Cambridge. A standardized definition of middle class, for example, could obscure some of those key facts.
In the social sciences, what’s needed instead of conceptual unity, Alexandrova says, is conceptual clarity.
Though social scientists disagree about how to go about solving this problem of clarity, Flake says that failure to tackle the issue jeopardizes the field as much as other crises rocking the discipline ( SN: 8/27/18 ). That’s because how a topic is defined determines the scales, surveys and other instruments used to study that concept. And that in turn shapes how researchers crunch numbers and arrive at conclusions.
Defining one’s key terms and then selecting the right tool is somewhat straightforward when relying on large, external datasets. For instance, instead of using national income databases, as is common in the study of the middle class, Haller and her team turned to the federal government’s Consumer Expenditure Surveys to understand people’s daily and emergency purchases.
But often social scientists, particularly psychologists, develop their own scales and surveys to quantify subjective concepts, such as self-esteem, mood or well-being. Definitions of those terms — and the instruments used to study them — can take on a life of their own, Flake says.
She and her team recently showed how this process plays out in the May-June American Psychologist . They combed through the 100 original studies and 100 replications included in a massive reproducibility project in psychology. The researchers zoomed in on 97 multi-item scales — measuring concepts such as gratitude, motivation and self-esteem — used in the original studies, and found that 54 of those scales had no citations to show where the scales originated. That suggests that the original authors defined their idea, and the tool used to measure that idea, on the fly , Flake says. Research teams then attempted to replicate 29 of those studies without digging into the scales’ sources, calling into question the meaning of their results.
For Flake, the way to achieve conceptual clarity is straightforward, if unlikely. Researchers must hit the brakes on generating new ideas, or replicating old ideas, and instead interrogate the morass of old ones.
She points to one promising, if labor-intensive, effort: the Psychological Science Accelerator , a collaboration of over 1,300 researchers in 84 countries. The project aims to identify big ideas in psychology, such as face perception and gender prejudice, and accumulate all the instruments and resulting data used to make sense of those ideas in order to discard, refine or combine existing definitions and tools.
“Instead of running replications, why don’t we use [this] massive team of researchers who represent a lot of perspectives around the world and review concepts first,” Flake says. “We need to stop replicating garbage.”
Sujata Gupta is the social sciences writer and is based in Burlington, Vt.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
