On a warm summer evening, a visitor to 1920s Göttingen, Germany, might have heard the hubbub of a party from an apartment on Friedländer Way. A glimpse through the window would reveal a gathering of scholars. The wine would be flowing and the air buzzing with conversations centered on mathematical problems of the day. The eavesdropper might eventually pick up a woman’s laugh cutting through the din: the hostess, Emmy Noether, a creative genius of mathematics.

At a time when women were considered intellectually inferior to men, Noether (pronounced NUR-ter) won the admiration of her male colleagues. She resolved a nagging puzzle in Albert Einstein’s newfound theory of gravity, the general theory of relativity. And in the process, she proved a revolutionary mathematical theorem that changed the way physicists study the universe.

It’s been a century since the July 23, 1918, unveiling of Noether’s famous theorem. Yet its importance persists today. “That theorem has been a guiding star to 20th and 21st century physics,” says theoretical physicist Frank Wilczek of MIT.

Noether was a leading mathematician of her day. In addition to her theorem, now simply called “Noether’s theorem,” she kick-started an entire discipline of mathematics called abstract algebra.
But in her career, Noether couldn’t catch a break. She labored unpaid for years after earning her Ph.D. Although she started working at the University of Göttingen in 1915, she was at first permitted to lecture only as an “assistant” under a male colleague’s name. She didn’t receive a salary until 1923. Ten years later, Noether was forced out of the job by the Nazi-led government: She was Jewish and was suspected of holding leftist political beliefs. Noether’s joyful mathematical soirees were extinguished.

She left for the United States to work at Bryn Mawr College in Pennsylvania. Less than two years later, she died of complications from surgery — before the importance of her theorem was fully recognized. She was 53.
Although most people have never heard of Noether, physicists sing her theorem’s praises. The theorem is “pervasive in everything we do,” says theoretical physicist Ruth Gregory of Durham University in England. Gregory, who has lectured on the importance of Noether’s work, studies gravity, a field in which Noether’s legacy looms large.

Making connections
Noether divined a link between two important concepts in physics: conservation laws and symmetries. A conservation law — conservation of energy, for example — states that a particular quantity must remain constant. No matter how hard we try, energy can’t be created or destroyed. The certainty of energy conservation helps physicists solve many problems, from calculating the speed of a ball rolling down a hill to understanding the processes of nuclear fusion.

Symmetries describe changes that can be made without altering how an object looks or acts. A sphere is perfectly symmetric: Rotate it any direction and it appears the same. Likewise, symmetries pervade the laws of physics: Equations don’t change in different places in time or space.
Noether’s theorem proclaims that every such symmetry has an associated conservation law, and vice versa — for every conservation law, there’s an associated symmetry.

Conservation of energy is tied to the fact that physics is the same today as it was yesterday. Likewise, conservation of momentum, the theorem says, is associated with the fact that physics is the same here as it is anywhere else in the universe. These connections reveal a rhyme and reason behind properties of the universe that seemed arbitrary before that relationship was known.
During the second half of the 20th century, Noether’s theorem became a foundation of the standard model of particle physics, which describes nature on tiny scales and predicted the existence of the Higgs boson, a particle discovered to much fanfare in 2012 (SN: 7/28/12, p. 5). Today, physicists are still formulating new theories that rely on Noether’s work.

When Noether died, Einstein wrote in the New York Times: “Noether was the most significant creative mathematical genius thus far produced since the higher education of women began.” It’s a hearty compliment. But Einstein’s praise alluded to Noether’s gender instead of recognizing that she also stood out among her male colleagues. Likewise, several mathematicians who eulogized her remarked on her “heavy build,” and one even commented on her sex life. Even those who admired Noether judged her by different standards than they judged men.

Symmetry leads the way
There’s something inherently appealing about symmetry (SN Online: 4/12/07). Some studies report that humans find symmetrical faces more beautiful than asymmetrical ones. The two halves of a face are nearly mirror images of each other, a property known as reflection symmetry. Art often exhibits symmetry, especially mosaics, textiles and stained-glass windows. Nature does, too: A typical snowflake, when rotated by 60 degrees, looks the same. Similar rotational symmetries appear in flowers, spider webs and sea urchins, to name a few.
But Noether’s theorem doesn’t directly apply to these familiar examples. That’s because the symmetries we see and admire around us are discrete; they hold only for certain values, for example, rotation by exactly 60 degrees for a snowflake. The symmetries relevant for Noether’s theorem, on the other hand, are continuous: They hold no matter how far you move in space or time.

One kind of continuous symmetry, known as translation symmetry, means that the laws of physics remain the same as we move about the cosmos.

The conservation laws that relate to each continuous symmetry are basic tools of physics. In physics classes, students are taught that energy is always conserved. When a billiard ball thwacks another, the energy of that first ball’s motion is divvied up. Some goes into the second ball’s motion, some generates sound or heat, and some energy remains with the first ball. But the total amount of energy remains the same — no matter what. Same goes for momentum.

These rules are taught as rote facts, but there’s a mathematical reason behind their existence. Energy conservation, according to Noether, comes from translation symmetry in time. Similarly, momentum conservation is due to translation symmetry in space. And conservation of angular momentum, the property that allows ice skaters to speed up their spins by hugging their arms close to their bodies, emerges from rotational symmetry, the idea that physics stays the same as we spin around in space.

In Einstein’s general theory of relativity, there is no absolute sense of time or space, and conservation laws become more difficult to comprehend. It’s that complexity that brought Noether to the topic in the first place.

Gravity gets Noether’d
In 1915, general relativity was a fascinating new theory. German mathematicians David Hilbert and Felix Klein, both at the University of Göttingen, were immersed in the new theory’s quirks. Hilbert had been competing with Einstein to develop the mathematically complex theory, which describes gravity as the result of matter curving spacetime (SN: 10/17/15, p. 16).

But Hilbert and Klein stumbled on a puzzle. Attempts to use the framework of general relativity to write an equation for conservation of energy resulted in a tautology: Like writing “0 equals 0,” the equation had no physical significance. This situation was a surprise to the pair; no previously accepted theories had energy conservation laws like this. The duo wanted to understand why general relativity had this peculiar feature.

The two recruited Noether, who had expertise in relevant areas of mathematics, to join them in Göttingen and help them solve the riddle.

Noether showed that the seemingly strange type of conservation law was inherent to a certain class of theories known as “generally covariant.” In such theories, the equations associated with the theory hold whether you’re moving steadily or accelerating wildly, because both sides of the theory’s equations change in sync. The result is that generally covariant theories — including general relativity — will always have these nontraditional conservation laws. This discovery is known as Noether’s second theorem.

This is what Noether did best: fitting specific concepts into their broader mathematical context. “She was just able to see what’s right at the heart of what’s going on and to generalize it,” says philosopher of science Katherine Brading of Duke University, who has studied Noether’s theorems.

On her way to proving the second theorem, Noether proved her first theorem, about the connection between symmetries and conservation laws. She presented both results in a July 23, 1918, lecture to the Göttingen Mathematical Society, and in a paper published in Göttinger Nachrichten.

It’s not easy to find quotes of Noether reflecting on the significance of her work. Once she made a discovery, she seemed to move on to the next thing. She referred to her own Ph.D. thesis as “crap,” or “Mist” in her native German. But Noether recognized that she changed mathematics: “My methods are really methods of working and thinking; this is why they have crept in everywhere anonymously,” she wrote to a colleague in 1931.

“Warm like a loaf of bread”
Born in 1882, Noether (her full name was Amalie Emmy Noether) was the daughter of mathematician Max Noether and Ida Amalia Noether. Growing up with three brothers in Erlangen, Germany, young Emmy’s mathematical talent was not obvious. However, she was known to solve puzzles that stumped other children.

At the University of Erlangen, where her father taught, women weren’t officially allowed as students, though they could audit classes with the permission of the professor. When the rule changed in 1904, Emmy Noether was quick to take advantage. She enrolled and earned her Ph.D. in 1907.
As a woman, Noether struggled to find a paid academic position, even after being recruited to the University of Göttingen. Her supporters there argued that her sex was irrelevant. “After all, we are a university and not a bathing establishment,” Hilbert reportedly quipped. But that wasn’t enough to get her a salary.

Although Göttingen finally began paying Noether in 1923, she never became a full-fledged professor. Hermann Weyl, a prominent mathematician at the university, said, “I was ashamed to occupy such a preferred position beside her whom I knew to be my superior as a mathematician in many respects.”

Noether took these knocks in stride. She was beloved for her buoyant personality. Weyl described her demeanor as “warm like a loaf of bread.”

She made a habit of taking long walks in the countryside with her students and colleagues, holding lengthy, math-fueled debates. When legs began to ache, Noether and company would plop down in a meadow and continue chatting. Sometimes she’d take students to her apartment for homemade “pudding à la Noether,” conversing until remnants of the dessert had dried on the dishes, according to a 1970 biography, Emmy Noether 1882–1935, by mathematical historian Auguste Dick.

When she landed at Bryn Mawr, Noether continued her research and taught classes of women — a change of pace from her previous students, who were known as “the Noether boys.” She also lectured at the Institute for Advanced Study in Princeton, N.J. Her death, less than two years after her 1935 arrival, left the academic community grieving.

Russian mathematician Pavel Aleksandrov called Noether “one of the most captivating human beings I have ever known,” and lamented the unfortunate circumstances of her employment. “Emmy Noether’s career was full of paradoxes, and will always stand as an example of shocking stagnancy and inability to overcome prejudice,” he said in 1935 at a meeting of the Moscow Mathematical Society.

Elusive partners
But Noether’s theorems remained relevant, particularly within particle physics. In the minute, enigmatic world of fundamental particles, teasing out what’s going on is difficult. “We have to rely on theoretical insight and concepts of beauty and aesthetics and symmetry to make guesses about how things might work,” Wilczek says. Noether’s theorems are a big help.

In particle physics, the relevant symmetries are hidden kinds known as gauge symmetries. One such symmetry is found in electromagnetism and results in the conservation of electric charge.

Gauge symmetry appears in the definition of electric voltage. A voltage — between two ends of a battery, for example — is the result of a difference in electric potential. The actual value of the electric potential itself doesn’t matter, only the difference.

This creates a symmetry in electric potential: Its overall value can be changed without affecting the voltage. This property explains why a bird can sit on a single power line without getting electrocuted, but if it simultaneously touches two wires at different electric potentials — bye-bye, birdie.

In the 1960s and ’70s, physicists extended this idea, finding other hidden symmetries associated with conservation laws to develop the standard model of particle physics.

“There’s this conceptual link that — once you realize it — you have a hammer and you go in search of nails to use it on,” Wilczek says. Anywhere they found a conservation law, physicists looked for a symmetry, and vice versa. The standard model, which Wilczek shared a 2004 Nobel Prize for his role in developing, explains a plethora of particles and their interactions. It is now considered by many physicists to be one of the most successful scientific theories ever, in terms of its ability to precisely predict the results of experiments.
At the Large Hadron Collider, at CERN in Geneva, physicists are still searching for new particles predicted using Noether’s insights. A hypothetical hidden symmetry, dubbed supersymmetry because it proposes another level of symmetry in particle physics, posits that each known particle has an elusive heavier partner.

So far, no such particles have been found, despite high hopes for their detection (SN: 10/1/16, p. 12). Some physicists are beginning to ask if supersymmetry is correct. Perhaps symmetry can only take physicists so far.

That notion is leaving some physicists in a bit of a lurch: “If that’s not going to be your guiding motto all the time — that more symmetry is better — then what will be your guiding motto?” asks mathematical physicist John Baez of the University of California, Riverside.

Holograms get symmetric
Despite such disappointments, symmetry maintains its luster in physics at large. Noether’s theorems are essential tools for developing potential theories of quantum gravity, which would unite two disparate theories: general relativity and quantum mechanics. Noether’s work helps scientists understand what kinds of symmetries can appear in such a unified theory.

One candidate relies on a proposed connection between two types of complementary theories: A quantum theory of particles on a two-dimensional surface without gravity can act as a hologram for a three-dimensional theory of quantum gravity in curved spacetime. That means the information contained in the 3-D universe can be imprinted on a surrounding 2-D surface (SN: 10/17/15, p. 28).

Picture a soda can with a label that describes the size and location of each bubble inside. The label catalogs how those bubbles merge and pop. A curious researcher could use the behavior of the can’s surface to understand goings-on inside the can, for example, calculating what might happen upon shaking it. For physicists, understanding a simpler, 2-D theory can help them comprehend a more complicated mess — namely, quantum gravity — going on inside. (The theory of quantum gravity for which this holographic principle holds is string theory, in which particles are described by wiggling strings.)
“Noether’s theorem is a very important part of that story,” says theoretical physicist Daniel Harlow of MIT. Symmetries in the 2-D quantum theory show up in the 3-D quantum gravity theory in a different context. In a satisfying twist, Noether’s first and second theorems become linked: Noether’s first theorem in the 2-D picture makes the same statement as Noether’s second theorem in 3-D. It’s like taking two sentences, one in Japanese and one in English, and realizing upon translating them that both say the same thing in different ways.

New directions for Noether
Everyday physics relies on Noether’s theorem as well. The conservation laws it implies help to explain waves on the surface of the ocean and air flowing over an airplane wing.

Simulating such systems helps scientists make predictions — about weather patterns, vibrations of bridges or the effects of a nuclear blast, for example. Noether’s theorem doesn’t automatically apply in computer simulations, which simplify the world by slicing it up into small chunks of space and time. So programmers have to manually add in conservation laws for energy and momentum.

“They throw away all of the physics, and then they have to try and force it all back in somehow,” says mathematician Elizabeth Mansfield of the University of Kent in England. But Mansfield has found new ways to make Noether’s theorem apply in simulations. She and colleagues have simulated a person beating a drum inside a simplified Stonehenge, determining how sound waves would wrap around the stone — while automatically conserving energy. Mansfield says her method, which she will present in September in London at a Noether celebration, could eventually be used to create simulations that behave more like the real world.

In addition to Noether’s importance in physics, in mathematics her ideas are so prominent that her name has become an adjective. References to Noetherian rings, Noetherian groups and Noetherian modules are sprinkled throughout current mathematical literature.

Noether’s work “should have been a wake-up call to society that women could do mathematics,” Gregory says. Eventually, society did awaken. In a 2015 lecture she gave about Noether at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, Gregory showed a slide of herself with five female colleagues, then at the center for particle theory at Durham University. While women in science still face challenges, no one in the group had to struggle to get paid for her work. “That is Noether’s legacy, and I honestly think she would have been really jazzed,” Gregory says. “I think this would have been her real … vindication.”

A heavy element’s nucleus is all bent out of shape.

Nobelium — element number 102 on the periodic table — has an atomic nucleus that is deformed into the shape of an American football, scientists report in the June 8 Physical Review Letters. The element is the heaviest yet to have its nucleus sized up.

By probing individual nobelium atoms with a laser, the team gauged the oblong shape of three nobelium isotopes: nobelium-252, -253 and -254. These different forms of the element each contain 102 protons, but varying numbers of neutrons. The shape is not uncommon for nuclei, but the researchers also determined that nobelium-252 and -254 contain fewer protons in the center of the nucleus than the outer regions — a weird configuration known as a “bubble nucleus” (SN: 11/26/16, p. 11).
The measurements are in agreement with previous theoretical predictions. “It nicely confirms what we believe,” says study coauthor Witold Nazarewicz, a theoretical nuclear physicist at Michigan State University in East Lansing.

Elements heavier than uranium, number 92, aren’t found in significant quantities in nature, and must be created artificially. Currently, the heaviest element on the periodic table is number 118, oganesson (SN Online: 2/12/18). But scientists hope to go even bigger, in search of a potential “island of stability,” a proposed realm in which elements are more stable than other heavy elements.

While many superheavy elements decay in just fractions of a second, some theoretical calculations suggest that elements inhabiting this proposed hinterland might persist longer, making them easier to study. Better understanding the heaviest known elements, including the shape of their atomic nuclei, could help scientists gauge what lies just out of reach.

New tech is revealing how young stars have an outsized influence on their environment. In this image from the Very Large Telescope in Chile, hundreds of newborn stars sculpt and illuminate gas and dust in their stellar nursery.

Released July 11 by the European Southern Observatory, the image shows star cluster RCW 38, which is located about 5,500 light-years from Earth toward the constellation Vela, in infrared light. Bright young stars shine in blue, while streams of cooler dust glow in darker red and orange. The stars are so bright and hot that their radiation pushes the dust and gas around them into intricate lacelike webs.
Previous pictures of this cluster taken in visible light were far less detailed, as the dust and gas blocked the stars’ light. But longer-wavelength infrared light can shine through the fog.

This image was taken while astronomers were testing a new observation system on the Chilean telescope, including an infrared imager called HAWK-I and a method to reduce blurriness called GRAAL. GRAAL projects four lasers onto the sky to act as artificial stars (SN: 6/14/03, p. 373), letting astronomers focus on a “star” of known brightness and subtract the fuzziness of Earth’s atmosphere. That adjustment lets astronomers bring the real star cluster into sharper focus.

When invasive rats chow down on island seabirds, coral reefs suffer.

Researchers studied islands with and without the rodents in the Chagos Archipelago in the Indian Ocean. On rat-free isles, there were on average 1,243 birds per hectare compared with about two birds per hectare on rat-infested islands, the team found. And these rodentless islands had healthier coral reef ecosystems. The secret: Bird poop, naturally rich in nitrogen, washes into the ocean and helps keep reefs productive, the scientists report in the July 12 Nature.
“We’re essentially linking three ecosystems in this study,” says study coauthor Nick Graham, an ecologist at Lancaster University in England. The rats affect the seabirds, which affect the reefs.

Introduced by humans to the Chagos Archipelago in the late 18th century, rats have since devastated native seabird populations, including red-footed boobies and terns. The rodents will eat seabird eggs, chicks and even the brains of adult birds, says Holly Jones, a restoration ecologist at Northern Illinois University in DeKalb who was not involved in the study. Rats are a major problem, Jones says, because seabirds are “ecosystem engineers.” When they’re gone, the environment on land and in the water changes dramatically.
Bird poop, or guano, is rich in certain heavy nitrogen isotopes — different forms of the element with the same amount of protons but varying numbers of neutrons — which come from the animals’ diet. Graham and his colleagues tested for these isotopes on 12 islands, six with rat infestations and six that had no rats, and in nearby coral reefs.
Compared with rat-infested islands, the team found much more of the heavy nitrogen in the soil of rat-free islands, where bird populations still thrived, and in the algae, sponges and fish in reefs that surrounded those islands. Bird guano is known to leach into the sea in rainwater or lapping waves, but its effects on reefs has been unclear.
The researchers now suspect the reefs around rat-free islands are healthier in part because nitrogen can act as a fertilizer for ocean plants and algae. More algae grow, leading to more fish grazing on the reefs and helping clear out dead corals, essential processes for a healthy reef. The fish that lived near reefs with more nitrogen also grew larger and faster, the scientists showed.

In addition to these indirect effects on reefs, nitrogen may also directly help the corals, says David Gillikin, a biogeochemist at Union College in Schenectady, N.Y., who was not involved in the study. Between 15 and 50 percent of nitrogen found in corals comes directly from seabird guano, he says.
Eradicating invasive rats from the islands will help preserve reefs, Graham says. Rat extermination has been done on 580 islands worldwide, with a success rate of about 85 percent.

Still, many coral reefs have been in trouble for decades and face various threats, including bleaching and ocean acidification, both consequences of climate change (SN: 5/12/18, p. 20). The UNESCO’s World Heritage Centre estimates that large coral reefs could be gone by the end of this century. “We’re constantly looking for solutions for the coral reef crisis,” Graham says.

Protecting seabirds to save coral reefs is one solution that doesn’t stink.

Painkillers crafted with a part of the wrinkle-smoothing drug Botox provide long-term pain relief in mice.

Researchers added the modified Botox to molecules that target pain-messaging nerve cells. Mice given a single spinal injection of the new drugs showed signs of pain relief for the full duration of the experiments, around three weeks, researchers report online July 18 in Science Translational Medicine. Such painkillers could potentially one day be developed for humans as alternatives to more addictive drugs, such as opioids.
Created by the bacterium Clostridium botulinum, botulinum toxin causes the food poisoning disease botulism. Botox, which is made from the toxin, is often injected into people to iron out worry lines and has been used to treat conditions that involve overactive muscles, such as repetitive neck spasms or overactive bladder (SN: 4/5/08, p. 213). The toxin has also been used to reduce the frequency of migraines.

Biochemist Bazbek Davletov of the University of Sheffield in England and colleagues focused on botulinum toxin because it can stop certain nerve cells from communicating with one another for up to five months with each injection. And “you locally inject less than a millionth of a gram, which is helpful to avoid any immune response,” he says.

Davletov and colleagues created their new drugs with a process he describes as a “molecular Lego system.” Taking the part of the botulinum toxin that blocks nerve cells from sending messages, the team attached the piece to one of two molecules that target neurons that relay pain information. The researchers removed the part of the toxin, found in Botox, that binds to muscle-controlling nerve cells.

In the new study, the scientists injected SP-BOT, a botulinum toxin-based pain reliever they’d made previously, into the spinal fluid of male mice with pain due to nerve damage. SP-BOT provided pain relief starting around three days after the injection and lasted through the rest of the experiment. In another experiment, SP-BOT also mollified pain from inflammation due to a different injury.
The researchers also created a new formula, called DERM-BOT, which targets nerve cell opioid receptors with dermorphin, a natural opioid secreted from the skin of a South American tree frog. DERM-BOT injected in mice with nerve damage kicked in right away and then provided pain relief to the rodents for over three weeks. The drug was also likewise effective in lessening pain from injuries that produced inflammation.

The team gauged the painkillers’ effectiveness by poking the animals’ paws with plastic filaments of different diameters. Mice in pain withdrew their paws from the finer filaments, Davletov says, while mice with pain relief didn’t withdraw until prodded by the thicker filaments, the same behavior seen in healthy mice.

Injecting the drugs into healthy mice caused no mobility issues, the researchers found, indicating that the drugs did not target muscle-controlling nerve cells as Botox does.

Neuroscientist Luana Colloca of the University of Maryland, Baltimore, who was not part of the study, says the drugs are promising candidates for further research in humans. Short-term painkillers, including morphine, may require multiple daily doses, and a body can build up tolerance and require higher doses for relief, she says. “One single administration lasting for several months can reduce the risk of dependence and addiction.”

But the drugs should be tested in female animals, Colloca adds. “We truly need to know if this data apply also to women in pain.”

An intergalactic race between light and a bizarre subatomic particle called a neutrino has ended in a draw.

The tie suggests that high-energy neutrinos, which are so lightweight they behave as if they’re massless, adhere to a basic rule of physics: Massless particles travel at the speed of light.

Comparing the arrival times of a neutrino and an associated blaze of high-energy light emitted from a bright, flaring galaxy (SN Online: 7/12/18) showed that the neutrino and light differed in speed by less than a billionth of a percent, physicists report in a paper posted July 13 at arXiv.org.
Massless particles — including the particles of light known as photons — consistently move about 300,000 kilometers per second, while massive particles move more slowly. Although neutrinos have mass, their heft is so infinitesimal that high-energy neutrinos travel at a rate effectively indistinguishable from that of light.

Some theories propose that a “spacetime foam” might slow particles of very high energies. The idea is that spacetime on extremely small scales is not smooth, but foamy. As a result, high-energy particles could get bogged down, as if moving through molasses. That effect could cause a significant difference between the speeds of the neutrino and the associated light, which would build up into a delay over the 4-billion-light-year trip from the neutrino’s home galaxy to Earth. But since the flare of light was spotted around the same time as the neutrino, there’s no evidence for such a discrepancy.

The result once again refutes a 2011 claim that neutrinos might travel faster than light. That measurement, made by a particle detector known as OPERA, was eventually determined to have been distorted by a loose cable (SN: 4/7/12, p. 9).

In the final frenzy of reproduction and death, social amoebas secrete proteins that help preserve a starter kit of food for its offspring.

Dictyostelium discoideum, a type of slime mold in soil, eats bacteria. Some wild forms of this species essentially farm the microbes, passing them along in spore cases that give the next generation of amoebas the beginnings of a fine local patch of prey. Tests find that the trick to keeping the parental immune system from killing this starter crop of bacteria is a surge of proteins called lectins, researchers say in the July 27 Science.
Lectins create a different way for the amoebas to treat bacteria: as actual symbionts inside cells, instead of as prey or infections, says study coauthor Adam Kuspa, a molecular cell biologist at Baylor College of Medicine in Houston. In a lab test of this ability, coating other bacteria with lectin derived from a plant allowed bacteria to slip inside cells from mice and survive as symbiotic residents.

The findings mark another chapter in a story that has been upending decades of what people thought they knew about social amoebas eating bacteria. The basic, almost alien, scenario is still true: D. discoideum amoebas, nicknamed Dicty, start life as single cells. When food dwindles, cells come together into a much bigger, multicellular slug-shaped creature with eight to 10 types of cells and the power to crawl. It then develops into something more like a fungus with a stalk holding up a case of spores, which start the next generation of amoebas.
Those casings, scientists once believed, held only spores. “For 70 years, we all thought that Dictyostelium development was sterile,” meaning no bacteria survived among spores, Kuspa says. “If you were not a very good microbiologist and contaminated your amoeba sample, one way to cure them of bacteria was to put them through a cycle of development.”
Then in 2011, researchers discovered that some Dicty strains are “farmers,” routinely packing live bacteria into spore cases, and jump-starting new bacterial livestock with each generation (SN: 2/12/11, p. 11). “That was a shock,” Kuspa says.

Researchers also discovered that the Dicty animal-like slug phase forms an immune system that kills bacteria, even as evidence grew that some bacteria had uses beyond food, such as providing defense chemistry. But how the slug avoided killing its own helpful bacteria was a mystery.

Comparing secretions of Dicty strains carrying bacteria versus strains that don’t showed a “dead-obvious” difference, Kuspa says: more lectins called discoidin A and discoidin C in the carrier forms. A series of tests supplying and withholding the proteins showed big effects on the fates of bacteria. The researchers found that the lectins raise the chances that bacteria can slip inside an amoeba cell and live hidden from immune-system sentinels that purge free-living intruders. That gives the bacteria a chance to end up in the spore case.

Lectins’ powers help make sense of how the startling discovery of bacterial farming fits with the revelation of social amoebas’ bacteria-killing immune systems. “Outstanding” work, says Debra Brock of Washington University in St. Louis, who studies both phenomena. “I love mechanisms.”

A new species of Ebola virus has been discovered in bats in Sierra Leone, the country’s government announced July 26. Researchers looking to identify new viruses before the pathogens spill over into human populations found the new Ebola strain while sampling bats in the northern Bombali district. This is the sixth known species of the virus.

RNA analysis of the virus revealed that it is “definitely related to other Ebola viruses,” says Tracey Goldstein, a pathologist at University of California, Davis, who is with the virus-hunting PREDICT project. “But [it] was quite different.”
Goldstein and her colleagues confirmed that the Bombali virus can infect human cells, but they still don’t know whether or not it can cause disease in people. “It has the machinery” to enter a human cell, she says, but that doesn’t mean that it can make people sick.

Some species of Ebola, such as the Reston virus, can cause disease in nonhuman primates but do not sicken humans. Other species of the virus however, like the Zaire virus, have been responsible for widespread epidemics, including a recent outbreak in the Democratic Republic of Congo that killed 33 people (SN Online: 5/18/18) and an earlier one responsible for more than 11,000 deaths across West Africa (SN: 1/24/15, p.12).

“We don’t really know where on the spectrum [the Bombali virus] stands,” Goldstein says. PREDICT and its partners are continuing to study the virus, and are educating people in the Bombali region to stay away from bats. At this point, Goldstein says, “I don’t think people should be alarmed.”

For nearly 60 years, scientists in Siberia have bred silver foxes in an attempt to replay how domestication occurred thousands of years ago. Now, in a first, researchers have compiled the genetic instruction book, or genome, of Vulpes vulpes, the red fox species that includes the silver-coated variant. This long-awaited study of the foxes’ DNA may reveal genetic changes that drove domestication of animals such as cats and dogs, the team reports online August 6 in Nature Ecology & Evolution.

At the Institute of Cytology and Genetics of the Russian Academy of Sciences in Novosibirsk, Russia, researchers bred one group of foxes for ever-tamer behavior, while another group was bred for increasing aggressiveness toward humans (SN: 5/13/17, p. 29). Rif, the male silver fox whose DNA serves as the example, or reference, genome for all members of the species, was the son of an aggressive vixen and a tame male.
Geneticist Anna Kukekova of the University of Illinois at Urbana-Champaign and colleagues also conducted less-detailed examinations of 30 foxes’ DNA: 10 foxes each from the tame and aggressive groups and 10 animals from a “conventional” group that hadn’t been bred for either friendliness or aggression.
Those genomes are an invaluable resource for researchers studying domestication, behavioral and population genetics and even human disorders such as autism and mental illness, says Ben Sacks, a canid evolutionary geneticist at the University of California, Davis, School of Veterinary Medicine. “It makes all kinds of research possible that weren’t before,” he says.
Domestication researchers want to pinpoint the genes that set tame foxes apart from conventionally bred and aggressive foxes because those genes may be the same ones that were altered in dogs and other domesticated animals. Kukekova and colleagues haven’t yet identified the precise genetic changes that led to the foxes’ tameness. But the team did find 103 regions of the genome where tame foxes tend to have one pattern of genetic variants and aggressive foxes are more likely to have a different pattern. Some of the regions contain multiple genes and DNA tweaks.
Narrowing the search to precise DNA changes will take more work, but the research is an important first step, says geneticist Elaine Ostrander, chief of the Cancer Genetics and Comparative Genomics Branch at the National Human Genome Research Institute in Bethesda, Md. She likens it to zooming in on a map.

“Before you get to the right house, you have to get to the right street. Before you can get to the right street, you have to get to the right city, state and so on,” she says. “It’s exciting that they’re to the right city at this point. Now they have to find the right addresses.” The list of 103 regions gives researchers clues about where to focus future studies, she says.

Many of the genes in the 103 regions are involved in brain development or function. In particular, the researchers found that a gene called SorCS1 is involved in making friendlier foxes. In people, some versions of the gene have been associated with autism or schizophrenia. Versions of that gene, which encodes a protein involved in transmitting chemical information between brain cells, determined whether foxes wanted to interact with humans “or never wanted to come close or see you again,” Kukekova says. One version of SorCS1 was found in 61 percent of tame foxes, but none of the aggressive foxes.
Other genes that differed between tame and aggressive foxes included ones involved in brain-cell signaling with the chemical messenger glutamate (SN Online: 5/15/13). Changes in these genes have also been associated with domestication in dogs, cats and rabbits.

Finding the same tweaked genes in studies of many different domesticated animals gives researchers confidence that they are closing in on the right answer, says evolutionary geneticist Krishna Veeramah of Stony Brook University in New York. But because of its long history and wealth of data, the fox study is the true test, he says. Having the same genes pop up in silver foxes “is incredibly encouraging that they are the real ones involved in domestication.”

Some lizards shed their still-wriggling tails to distract predators, but sea cucumbers take this sort of strategy to the next level. Some startled sea cucumbers shoot a silky — and sticky — substance out of their rear ends that is actually an entire organ.

The tangle of tubules looks like intestines, but it evolved from the invertebrates’ respiratory system, and, like lizard tails, it regenerates after use. In a new study in the April 10 Proceedings of the National Academy of Sciences, researchers delved into the black sea cucumber’s genome to see how the stringlike tubules, called the Cuvierian organ, work at the molecular level.
The black sea cucumber (Holothuria leucospilota) is “the most dominant sea cucumber species in the South China Sea,” says Ting Chen, a biologist at the South China Sea Institute of Oceanology in Guangzhou. “We would like to know what evolutionary advantage this sea cucumber has gained … so that its population can expand so widely and predominantly.”
So the team analyzed the sea cucumber’s entire genome, or genetic instruction book, and focused on genes from the Cuvierian organ because it’s such an odd structure. Then the team predicted what proteins would be made from Cuvierian organ genes using a program called AlphaFold (SN: 9/23/22). Some unexpected predicted proteins were new types of receptors on cells’ surfaces that may play a role in expelling the organ.

The team also found that the “silk” proteins of sea cucumbers’ tubules don’t contain the same sequences of amino acids seen in spider silk, but are similarly made up of long repeated chains of amino acids. This finding hints that these long repeats might be a shared structure across silklike proteins, even when those proteins evolved independently.

What’s more, Chen says, is that the organ’s stickiness — which stops sea cucumber predators like fish, crabs and starfish in their tracks — comes from proteins that have features similar to amyloids. Amyloids are associated with many diseases in humans, including neurodegenerative conditions like Alzheimer’s (SN: 9/9/15).

This paper not only highlights unexpected proteins that are specific to the Cuvierian tubules, says Patrick Flammang, a biologist at the University of Mons in Belgium who was not involved with the study. It also provides a lot of data that can be used to answer other questions about how the enigmatic organ evolved, he says.

And the usefulness of a high-quality genome doesn’t stop there. “We need genomic data for our studies on the reproductive, endocrine, immune and digestive systems of H. leucospilota,” Chen says. The team, he says, is now investigating the genetics behind how the sea cucumbers detect light and digest food.

A good genome, Flammang says, is “a cornerstone to be able to do this work.”