Transistors, the building blocks of modern electronics, are typically made of silicon. Because it’s a semiconductor, this material can control the flow of electricity in a circuit. But silicon has fundamental physical limits that restrict how compact and energy-efficient a transistor can be.

MIT researchers have now replaced silicon with a magnetic semiconductor, creating a magnetic transistor that could enable smaller, faster, and more energy-efficient circuits. The material’s magnetism strongly influences its electronic behavior, leading to more efficient control of the flow of electricity. 

The team used a novel magnetic material and an optimization process that reduces the material’s defects, which boosts the transistor’s performance.

The material’s unique magnetic properties also allow for transistors with built-in memory, which would simplify circuit design and unlock new applications for high-performance electronics.

“People have known about magnets for thousands of years, but there are very limited ways to incorporate magnetism into electronics. We have shown a new way to efficiently utilize magnetism that opens up a lot of possibilities for future applications and research,” says Chung-Tao Chou, an MIT graduate student in the departments of Electrical Engineering and Computer Science (EECS) and Physics, and co-lead author of a paper on this advance.

Chou is joined on the paper by co-lead author Eugene Park, a graduate student in the Department of Materials Science and Engineering (DMSE); Julian Klein, a DMSE research scientist; Josep Ingla-Aynes, a postdoc in the MIT Plasma Science and Fusion Center; Jagadeesh S. Moodera, a senior research scientist in the Department of Physics; and senior authors Frances Ross, TDK Professor in DMSE; and Luqiao Liu, an associate professor in EECS, and a member of the Research Laboratory of Electronics; as well as others at the University of Chemistry and Technology in Prague. The paper appears today in Physical Review Letters.

Overcoming the limits

In an electronic device, silicon semiconductor transistors act like tiny light switches that turn a circuit on and off, or amplify weak signals in a communication system. They do this using a small input voltage.

But a fundamental physical limit of silicon semiconductors prevents a transistor from operating below a certain voltage, which hinders its energy efficiency.

To make more efficient electronics, researchers have spent decades working toward magnetic transistors that utilize electron spin to control the flow of electricity. Electron spin is a fundamental property that enables electrons to behave like tiny magnets.

So far, scientists have mostly been limited to using certain magnetic materials. These lack the favorable electronic properties of semiconductors, constraining device performance.

“In this work, we combine magnetism and semiconductor physics to realize useful spintronic devices,” Liu says.

The researchers replace the silicon in the surface layer of a transistor with chromium sulfur bromide, a two-dimensional material that acts as a magnetic semiconductor.

Due to the material’s structure, researchers can switch between two magnetic states very cleanly. This makes it ideal for use in a transistor that smoothly switches between “on” and “off.”

“One of the biggest challenges we faced was finding the right material. We tried many other materials that didn’t work,” Chou says.

They discovered that changing these magnetic states modifies the material’s electronic properties, enabling low-energy operation. And unlike many other 2D materials, chromium sulfur bromide remains stable in air.

To make a transistor, the researchers pattern electrodes onto a silicon substrate, then carefully align and transfer the 2D material on top. They use tape to pick up a tiny piece of material, only a few tens of nanometers thick, and place it onto the substrate.

“A lot of researchers will use solvents or glue to do the transfer, but transistors require a very clean surface. We eliminate all those risks by simplifying this step,” Chou says.

Leveraging magnetism

This lack of contamination enables their device to outperform existing magnetic transistors. Most others can only create a weak magnetic effect, changing the flow of current by a few percent or less. Their new transistor can switch or amplify the electric current by a factor of 10.

They use an external magnetic field to change the magnetic state of the material, switching the transistor using significantly less energy than would usually be required.

The material also allows them to control the magnetic states with electric current. This is important because engineers cannot apply magnetic fields to individual transistors in an electronic device. They need to control each one electrically.

The material’s magnetic properties could also enable transistors with built-in memory, simplifying the design of logic or memory circuits.

A typical memory device has a magnetic cell to store information and a transistor to read it out. Their method can combine both into one magnetic transistor.

“Now, not only are transistors turning on and off, they are also remembering information. And because we can switch the transistor with greater magnitude, the signal is much stronger so we can read out the information faster, and in a much more reliable way,” Liu says.

Building on this demonstration, the researchers plan to further study the use of electrical current to control the device. They are also working to make their method scalable so they can fabricate arrays of transistors.

This research was supported, in part, by the Semiconductor Research Corporation, the U.S. Defense Advanced Research Projects Agency (DARPA), the U.S. National Science Foundation (NSF), the U.S. Department of Energy, the U.S. Army Research Office, and the Czech Ministry of Education, Youth, and Sports. The work was partially carried out at the MIT.nano facilities.

Someone pleaded guilty to secretly working for a ransomware gang as he negotiated ransomware payments for clients.

A first-of-its-kind conference that focused on phasing out fossil fuels now confronts the challenge of turning plans into policy.

The judge rejected the oil industry's argument that federal law bars the tribes from suing under state law.

The probe comes amid a legal push by cities, counties and states to hold fossil fuel companies financially accountable for climate change.

Administration officials say Tehran is days from crisis, but analysts see a slower squeeze with global price shocks already hitting U.S. consumers and reshaping the political fight.

The cash infusion comes at a time of uncertainty for climate tech startups as private and federal funding shrinks.

Advocates are trying to block fossil fuel projects in energy-hungry Asia by convincing insurers not to cover or invest in them.

Dangerous combinations of hurricanes, heat and drought are making fires more likely.

The soaring price of oil and gas has forced governments across the globe to rethink their energy security policies.

Silicon Ranch believes cattle-grazing is the next frontier in so-called agrivoltaics.

The controversy has embroiled buyers of the $7 billion in sustainable bonds the country has issued since 2022 across U.S. dollar, euro and yen markets.

There are other significant obstacles facing the construction, including ongoing negotiations between the Alberta and federal governments over a climate emissions framework.

Nature Climate Change, Published online: 01 May 2026; doi:10.1038/s41558-026-02628-7

Addressing non-CO2 greenhouse gases alongside CO2 is essential for climate mitigation, but distributional effects remain a major concern. Now a study shows that when climate policy extends beyond CO2, the resulting costs are unevenly distributed across households worldwide.

Nature Climate Change, Published online: 01 May 2026; doi:10.1038/s41558-026-02622-z

In response to the large contribution of non-CO2 GHG to global warming, pricing of their emissions has been proposed as a cost-effective mitigation option. The authors find that such multi-GHG pricing can be more regressive than CO2-only pricing, with a relative increase in burden for low-income households.

For the last couple of years, we’ve watched the same predictable cycle play out across the globe: a state (or country) passes a clunky age-verification mandate, and, without fail, Virtual Private Network (VPN) usage surges as residents scramble to maintain their privacy and anonymity. We've seen this everywhere—from states like Florida, Missouri, Texas, and Utah, to countries like the United Kingdom, Australia, and Indonesia. 

Instead of realizing that mass surveillance and age gates aren't exactly crowd favorites, Utah lawmakers have decided that VPNs themselves are the real issue.

Next week, on May 6, 2026, Utah will become, to EFF’s knowledge, the first state in the nation to target the use of VPNs to avoid legally mandated age-verification gates. While advocates in states like Wisconsin successfully forced the removal of similar provisions due to constitutional and technical concerns, Utah is proceeding with a mandate that threatens to significantly undermine digital privacy rights. 

What the Bill Does

Formally known as the “Online Age Verification Amendments,” Senate Bill 73 (SB 73) was signed by Governor Spencer Cox on March 19, 2026. While the majority of the bill consists of provisions related to a 2% tax on revenues from online adult content that is set to take effect in October, one of the more immediate concerns for EFF is the section regulating VPN access, which goes into effect this coming Wednesday.

The VPN Provisions

The new law explicitly addresses VPN use in Section 14, which amends Section 78B-3-1002 of existing Utah statutes in two primary ways:

1. Regulation based on physical location: Under the law, an individual is considered to be accessing a website from Utah if they are physically located there, regardless of whether they use a VPN, proxy server, or other means to disguise their geographic location.
2. Ban on sharing VPN instructions: Commercial entities that host "a substantial portion of material harmful to minors" are now prohibited from facilitating or encouraging the use of a VPN to bypass age checks. This includes providing instructions on how to use a VPN or providing the means to circumvent geofencing.

By holding companies liable for verifying the age of anyone physically in Utah, even those using a VPN, the law creates a massive "liability trap." Just like we argued in the case of the Wisconsin bill, if a website cannot reliably detect a VPN user's true location and the law requires it to do so for all users in a particular state, then the legal risk could push the site to either ban all known VPN IPs, or to mandate age verification for every visitor globally. This would subject millions of users to invasive identity checks or blocks to their VPN use, regardless of where they actually live. 

"Don't Ask, Don't Tell"

In practice, SB 73 is different from the Wisconsin proposal in that it stops short of a total VPN ban. Instead, it discourages using VPNs by imposing the liability described above and by muzzling the websites themselves from sharing information about VPNs. This raises significant First Amendment concerns, as it prevents platforms from providing basic, truthful information about a lawful privacy tool to their users. 

Unlike previous drafts seen in other states, SB 73 doesn't explicitly ban the use of a VPN. Under a "don't ask, don't tell" style of enforcement, websites likely only have an obligation to ask for proof of age if they actually learn that a user is physically in Utah and using a VPN. If a site doesn’t know a user is in Utah, their broader obligation to police VPNs remains murky. So, while SB 73 isn’t as extreme as the discarded Wisconsin proposal, it remains a dangerous precedent.

Technical Feasibility

Then there is also the question of technical feasibility: Blocking all known VPN and proxy IP addresses is a technical whack-a-mole that likely no company can win. Providers add new IP addresses constantly, and no comprehensive blocklist exists. Complying with Utah’s requirements would require impossible technical feats.

The internet is built to, and will always, route around censorship. If Utah successfully hampers commercial VPN providers, motivated users will transition to non-commercial proxies, private tunnels through cloud services like AWS, or residential proxies that are virtually indistinguishable from standard home traffic. These workarounds will emerge within hours of the law taking effect. Meanwhile, the collateral damage will fall on businesses, journalists, and survivors of abuse who rely on commercial VPNs for essential data security.

These provisions won't stop a tech-savvy teenager, but they certainly will impact the privacy of every regular Utah resident who just wants to keep their data out of the hands of brokers or malicious actors.

Uncharted Territory

Lawmakers have watched age-verification mandates fail and, instead of reconsidering the approach, have decided to wage war on privacy itself. As the Cato Institute states: 

“The point is that when an internet policy can be avoided by a relatively common technology that often provides significant privacy and security benefits, maybe the policy is the problem. Age verification regimes do plenty of damage to online speech and privacy, but attacking VPNs to try to keep them from being circumvented is doubling down on this damaging approach."

Attacks on VPNs are, at their core, attacks on the tools that enable digital privacy. Utah is setting a precedent that prioritizes government control over the fundamental architecture of a private and secure internet, and it won’t stop at the state’s borders. Regulators in countries outside the U.S. are still eyeing VPN restrictions, with the UK Children’s Commissioner calling VPNs a “loophole that needs closing” and the French Minister Delegate for Artificial Intelligence and Digital Affairs saying VPNs are “the next topic on my list” after the country enacted a ban on social media for kids under 15.

As this law goes into effect next week, we are entering uncharted territory. Lawmakers who can’t distinguish between a security tool and a "loophole" are now writing the rules for one of the most complex infrastructures on Earth. And we can assure that the result won't be a safer internet, only an increasingly less private one.

GPS navigation, cryptography, quantum computing — while some of humankind’s greatest advancements have been invented by pioneers from various cultures, they were founded upon one common grammar: mathematics.

“Mathematics is the language with which God wrote the universe,” said the famous Italian astronomer, physicist, and philosopher Galileo Galilei, who, among his various scientific contributions, helped provide evidence for the idea that the sun is at the center of the solar system.

Although mostly conveyed through combinations of numbers, letters, and signs that may seem enigmatic to many, math equations hold within them countless stories — playbooks that generations of wonderers and inventors have crafted, refined, and shared in an attempt to make sense of a world full of unknown variables.

“I have faith in mathematics that, when there seems to be something special happening, when there’s some coincidence, that it’s not just a coincidence,” says mathematician Amanda Burcroff, “but that there’s actually some really deep, interesting, and involved reason for why that should be true.”

Burcroff’s research is focused on algebraic combinatorics, an area that provides discrete frameworks for understanding algebraic and geometric spaces that ubiquitously arise across science. This year, she joins MIT’s Department of Mathematics as a postdoc as part of the School of Science Dean’s Fellowship. Working with Professor Alexander Postnikov, Burcroff is building upon her techniques with the goal of applying them to other areas such as theoretical physics — a field that seeks to uncover the fundamental laws governing everything from subatomic particles to the cosmos itself.

“I have trust that if you keep following the path, eventually you’ll find the treasure — that is, whatever theorem or proof — that you’re looking for,” she says.

Exploring possibilities and redefining rules

Like many children, Burcroff once saw math as a subject that entailed lots of memorizing. Although she felt that it came naturally to her, she didn’t always find math very interesting.

In high school, as she came to learn about areas like calculus and geometry, Burcroff started to see the discipline in a different light — a creative approach to exploring what’s possible.

“[In] most other fields, the rules are imposed on you by the world,” she says, “but in math, you get full freedom to lay down those rules and then figure out what the implications of those rules are by using logical consequence.”

In 2015, Burcroff began her bachelor’s degree at the University of Michigan with a major in math and a minor in computer science. There, she entered the world of combinatorics — a branch of math dealing with counting, arranging, and combining objects that forms a crucial basis for understanding the complexity of problems, as well as the limits of computer algorithms.

“When I was starting out, I was just happy to have any mystery that anyone gave me,” she says.

Math was, to Burcroff, like a fun game with levels to complete. But during a study abroad program in Budapest, Hungary — the hometown of Paul Erdős, who is considered to be one of the most prolific mathematicians of the 20th century — it became more exciting to play when she was handed puzzles no one has yet solved.

“It turns out that if you put down the right set of rules, there’s an infinite number of beautiful things that you can do with it,” she says.

A journey of endless mysteries to unlock

In 2019, Burcroff embarked on a journey to pursue further research in England, later completing a master’s degree in pure mathematics at the University of Cambridge, then a research master’s degree at Durham University. In 2021, she returned to the United States and began her PhD at Harvard University, with the guidance of Professor Lauren Williams.

Among several riddles she has unraveled over the years, Burcroff helped unify different mathematical approaches to understand why systems work so reliably. Think of it as finding out that two seemingly different set of instructions actually lead the same way. By demonstrating their connections, her work has revealed an underlying, overarching mathematical architecture — a finding that later helped Burcroff and her collaborators tackle one of the many enduring riddles in her field.

Generalized cluster algebras form the basis for describing geometries that appear throughout physics. For more than a decade, mathematicians suspected these building blocks were created only by adding up ingredients and never subtracting, although no one was able to prove it. In 2024, Burcroff and her collaborators published a paper demonstrating that these spaces have nice positivity properties by developing a new way to count and organize patterns — helping untangle a long-standing conjecture, whose potential implications span from predicting particle collision outcomes to describing the spaces appearing in string theory.

These findings have earned Burcroff numerous prestigious awards including a National Science Foundation Graduate Research Fellowship, a British Marshall Scholarship, and a Jack Kent Cooke Graduate Fellowship.

Despite the tremendous number of problems she has answered, new ones keep arising.

“Every time you unlock one of them, it gives you a bunch of paths to new connected mysteries,” Burcroff says.

At MIT, she is working with Postnikov, whose research on combinatorics and positivity-type problems has presented a radically different way to calculate fundamental quantities in quantum field theory.

“Burcroff is conducting research across disciplinary boundaries,” says Postnikov.

He adds: “I am sure that she will have a lot of fruitful interactions with researchers in other MIT departments.”

Burcroff’s goal is to apply combinatorial techniques to broader physical contexts and direct applications, especially those with implications to topics like mirror symmetry, a principle in string theory suggesting that very different-looking geometric spaces can be mathematically equivalent.

While “doing math is 99 percent trying something and failing,” Burcroff says it is this same challenge that keeps her motivated. To her, it is not about reaching a destination, but rather about the continuous “process of discovery,” one she hopes to share beyond the typical classroom.

To make math more accessible, especially among underrepresented groups, Burcroff has worked with mentorship programs including Harvard’s Real Representations and Math Includes, Cambridge Girls’ Angle, and MIT PRIMES. During her time as a postdoc, she hopes to continue this outreach and explore ways to get involved with other support groups at MIT’s Department of Mathematics.

When a gene is turned on in a cell, it creates a ripple effect along the DNA strand, changing the physical structure of the strand. A new study by MIT researchers shows that these ripples can stimulate or suppress neighboring genes.

These effects, which result from the winding or unwinding of neighboring DNA, are determined by the order of genes along a strand of DNA. Genes upstream of the active gene are usually turned up, while those downstream are inhibited.

The new findings offer guidance that could make it easier to control the output of synthetic gene circuits. By altering the relative ordering and arrangement of genes, or “gene syntax,” researchers could create circuits that synergize to maximize their output, or that alternate the output of two different genes.

“This is really exciting because we can coordinate gene expression in ways that just weren’t possible before,” says Katie Galloway, an assistant professor of chemical engineering at MIT. “Syntax will be really useful for dynamic circuits. Now we have the ability to select not only the biochemistry of circuits, but also the physical design to support dynamics.”

Galloway is the senior author of the study, which appears today in Science. MIT postdoc Christopher Johnstone PhD ’26 is the paper’s lead author. Other authors include MIT graduate student Kasey Love, members of the lab of Brandon DeKosky, an MIT associate professor of chemical engineering, and researchers from Peter Zandsta’s lab at the University of British Columbia and the labs of Christine Mummery and Richard Davis at Leiden University Medical Center in the Netherlands.

Gene syntax

When a gene is copied into messenger RNA, or “transcribed,” the double-stranded DNA helix must be unwound so that an enzyme called RNA polymerase can access the DNA and start copying it. That unwinding leads to physical changes in the structure of DNA strand.

Upstream of the gene, DNA becomes looser, while downstream, it becomes more tightly wound. These changes affect RNA polymerase’s ability to access the DNA: Upstream of an active gene, it’s easier for the enzyme to attach; downstream, it’s more difficult.

In a study published in 2022, Galloway and Johnstone performed computational modeling that explored how these biophysical changes might influence gene expression. They studied three different arrangements, or types of syntax: tandem, divergent, and convergent.

Most synthetic gene circuits are designed in a tandem arrangement, with one gene followed by another downstream. In a divergent arrangement, neighboring genes are transcribed in opposite directions (away from each other), and in convergent syntax, they are transcribed toward each other.

The modeling suggested that the divergent arrangement was most likely to produce circuits where both genes are expressed at a high level. Tandem arrangements were predicted to result in the downstream gene being suppressed by the upstream gene.In the new study, the researchers wanted to see if they could observe these predicted phenomena in human cells.

“Normally, we think about gene circuits and pieces of DNA as these lines that we draw, but they’re polymers that have physical characteristics,” Galloway says. “The thing that we were trying to solve in this paper was: When you put two genes on the same piece of DNA, how does their physical interaction become coupled?”

The researchers engineered circuits that each contained two genes, in either a tandem, divergent, or convergent configuration, into human cell lines and human induced pluripotent stem cells.

The results confirmed what their modeling had predicted: In divergent circuits, expression of both genes was amplified. In tandem circuits, turning on the upstream gene suppressed the expression of the downstream gene.

These effects produced as much as a 25-fold increase or decrease in gene expression, and they could be seen at distances of up to 2,000 base pairs between genes.

Using a high-resolution genome mapping technique called Region Capture Micro-C, the researchers were also able to analyze how the DNA structure changed when nearby genes were being transcribed.

As predicted, they found that the DNA regions downstream from an active gene formed tightly twisted structures known as plectonemes, similar to the tangles seen in a twisted telephone cord. These structures make it harder for RNA polymerase to bind to DNA.

To engineer these cells, the researchers used a new system they developed with the LUMC team called STRAIGHT-IN Dual, which allows them to efficiently insert two genes into the same DNA strand at both alleles. This system is being reported in a second paper published today, in Nature Biomedical Engineering.

Precise control

The new findings could help guide the design of synthetic gene circuits, which are usually designed to be controlled by biochemical interactions with activator or repressor molecules. Now, circuit designers can also perform biophysical manipulations to enhance or repress genes expression.

“Everyone thinks about the components they need, and the biochemical properties they need to build a circuit,” Galloway says. “Now, we have added the physical construction of those components, which is going to change how those biochemical units are interpreted.”

As a demonstration of one potential application, the researchers built synthetic circuits containing the genes for two segments of a novel antibody discovered by the Dekosky lab, used to treat yellow fever, and incorporated them into human cells. As they expected, the divergent syntax produced larger quantities of the yellow fever antibody.

Galloway’s lab has also used this approach to optimize the output of synthetic gene circuits they previously reported that could be used to deliver gene therapy or to reprogram adult cells into other cell types.

This strategy could also be used to build a variety of other types of dynamic synthetic circuits, such as toggle switches, oscillators, or pulse generators, for any application that requires precise control over gene expression.

“If you want coordinated expression, a divergent circuit is great. If you want something that’s either/or, you can imagine using a convergent or tandem circuit, so when one turns on, the other turns off, and you can alternate pulses,” Galloway says. “Now that we understand the syntax, I think this will pave the way for us to program dynamic behaviors.”

The research was funded, in part, by the National Institutes of Health, the National Institute for General Medical Sciences, a National Science Foundation CAREER Award, the Pershing Square Foundation, the Air Force Research Laboratory, and the Koch Institute Support (core) Grant from the National Cancer Institute.

Materials called relaxor ferroelectrics have been used for decades in technologies like ultrasounds, microphones, and sonar systems. Their unique properties come from their atomic structure, but that structure has stubbornly eluded direct measurement.

Now a team of researchers from MIT and elsewhere has directly characterized the three-dimensional atomic structure of a relaxor ferroelectric for the first time. The findings, reported today in Science, provide a framework for refining models used to design next-generation computing, energy, and sensing devices.

“Now that we have a better understanding of exactly what’s going on, we can better predict and engineer the properties we want materials to achieve,” says corresponding author James LeBeau, MIT’s Kyocera Professor of Materials Science and Engineering. “The research community is still developing methods to engineer these materials, but in order to predict the properties those materials will have, you have to know if your model is right.”

In their paper, the researchers describe how they used an emerging technique to reveal the distribution of electric charges in the material, with a surprising result.

“We realized the chemical disorder we observed in our experiments was not fully considered previously,” says co-first authors Michael Xu PhD ’25 and Menglin Zhu, who are both postdocs at MIT. “Working with our collaborators, we were able to merge the experimental observations with simulations to refine the models and better predict what we see in experiments.”

Joining Zhu, Xu, and LeBeau on the paper are Colin Gilgenbach and Bridget R. Denzer, MIT PhD students in materials science and engineering; Yubo Qi, an assistant professor at the University of Alabama at Birmingham; Jieun Kim, an assistant professor at the Korea Advanced Institute of Science and Technology; Jiahao Zhang, a former PhD student at the University of Pennsylvania; Lane W. Martin, a professor at Rice University; and Andrew M. Rappe, a professor at the University of Pennsylvania.

Probing disordered materials

Leading simulations of relaxor ferroelectrics suggest that when an electric field is applied, the interactions of positively and negatively charged atoms in different nanoregions of the material help give rise to exceptional energy storage and sensing capabilities. The details of those nanoregions have been impossible to directly measure to date.

For their Science paper, the researchers studied a relaxor ferroelectric material used in sensors, actuators, and defense systems that is a lead magnesium niobate-lead titanate alloy. They used an emerging measurement technique, called multi-slice electron ptychography (MEP), in which researchers move a nanoscale-sized probe of high-energy electrons over a material and measure the resulting electron diffraction patterns.

“We do this in a sequential way, and at each position, we acquire a diffraction pattern,” Zhu explains. “That creates regions of overlap, and that overlap has enough information to use an algorithm to iteratively reconstruct three-dimensional information about the object and the electron wave function.”

The technique revealed a hierarchy of chemical and polar structures that spanned from atomic to mesoscopic scales. The researchers also found that many regions of differing polarization in the material were much smaller than predicted by the leading simulations. The researchers then fed their new data back into those computer simulations and refined the models to better reflect their findings under different conditions.

“Previously, these models basically had random regions of polarization, but they didn’t tell you how those regions correlate with each other,” Xu says. “Now we can tell you that information, and we can see how individual chemical species modulate polarization depending on the charge state of atoms.”

Toward better materials

Zhu says the paper demonstrates the potential of electron ptychography to study complex materials and opens up new avenues of research into complex, disordered materials.

“This study is the first time in the electron microscope that we’ve been able to directly connect the three-dimensional polar structure of relaxor ferroelectrics with molecular dynamics calculations,” Xu says. “It further proves you can get three-dimensional information out of the sample using this technique.”

The researchers also believe the approach could one day help engineer materials with advanced electronic behaviors for a range of improved memory storage, sensing, and energy technologies.

“Materials science is incorporating more complexity into the material design process — whether that’s for metal alloys or semiconductors — as AI has improved and our computational tools have become more advanced,” LeBeau says. “But if our models aren’t accurate enough and we have no way to validate them, it’s garbage in garbage out. This technique helps us understand why the material behaves the way it does and validate our models.”

The work was supported, in part, by the U.S. Army Research Laboratory, the U.S. Office of Naval Research, the U.S. Department of War, and a National Science Graduate Fellowship. The researchers also used MIT.nano facilities.

Recent studies suggest animals and people alike have close and complex relationships with the bacteria around and within them. The human gut microbiome, for instance, has been associated with both depression and Parkinson’s disease. To go beyond association toward understanding of the actual mechanisms that enable the bacterial microbiome to influence brain function, a new study by neuroscientists in The Picower Institute for Learning and Memory at MIT examines the mechanisms at work in a model “bacterial specialist,” the nematode Caenorhabditis elegans.

In the new study in Current Biology, the team, led by Picower Fellow Cassi Estrem in the Picower Institute for Learning and Memory lab of Associate Professor Steven Flavell, identifies the specific chemicals that a key neuron in C. elegans senses, both in the bacteria that it eats and in the bacteria that it needs to avoid ingesting.

“In our bodies, our own cells are outnumbered by the bacterial cells living in and on us. There’s an increasing recognition that this has a profound impact on human health,” says Flavell, an investigator of the Howard Hughes Medical Institute and faculty member of MIT’s Department of Brain and Cognitive Sciences. “It’s been clear that there are links for some time. Our study aimed to identify the hard mechanisms of how a host nervous system is affected by bacteria in the alimentary canal.”

Achieving a fundamental mechanistic understanding of how neurons interact with bacteria could help improve attempts to intervene in or manipulate those interactions with therapeutic drugs or supplements, Flavell says.

Mmm … sugar

Flavell calls C. elegans a “bacterial specialist” because the tiny, transparent worm has evolved to eat bacteria as its diet, while also needing to avoid pathogenic bacteria that can prove to be its undoing. This has led it to develop a nervous system especially well-attuned to sorting out what is food and what is foe. In 2019, the lab discovered that the neuron NSM, which projects into the worm’s alimentary canal, employs two “acid sensing ion channels” (ASICs) to detect when certain bacteria have been ingested. Notably, those ion channels are analogous to ones found in neurons in humans. When NSM detects yummy bacteria, it releases serotonin that causes the worm to increase its feeding rate and slow its slithering so that it can stay to dine on the surrounding meal.

To really understand how this works, Flavell and Estrem realized they needed to know exactly what the ion channels are detecting in the bacteria. To get started, they exposed worms to 20 different kinds of bacteria the worms are known to encounter and found that they all activated NSM activity to varying extents. Then they broke the bacteria down into more and more specific chemical components to see which one or ones triggered NSM. The experiments ruled out many components, including DNA, lipids, proteins, and simple sugars, and instead found that it’s specifically the polysaccharide sugars that coat many bacteria that drive NSM activation. In particular, in gram-positive bacteria, a chemical called peptidoglycan activated NSM. In gram-negative bacteria, a different polysaccharide was apparently in play.

Estrem and Flavell’s team also ran experiments showing that polysaccharides from bacteria in general, and peptidoglycan in particular, not only trigger NSM electrical activity, but actually promote the feeding and slowing behaviors. They also showed that genetically knocking out the ASICs abolished these responses. In all, they demonstrated that polysaccharide and peptidoglycan detection are sufficient to trigger the worm’s behaviors, and requires the ASICs.

Better not eat this

Having shown what exactly triggers the worms to recognize their bacterial food, the researchers wondered whether they could also pinpoint a danger sign the worm finds in harmful bacteria. For these experiments, they carefully used Serratia marcescens, a bacterium that’s also infectious for humans. Some strains of the bacteria have a red color, while others do not. The red ones, which have a pigment called prodigiosin, tend to be much more lethal for worms. In their testing, the researchers found that when NSM detected the non-pigmented bacteria, the neuron still activated and the worms still ingested the bacteria, but when prodigiosin was present, NSM did not activate and the worm did not pump it in or slow down to eat.

Adding prodigiosin to normally yummy bacteria also suppressed NSM’s usual response. In other words, the worms have evolved their digestive behavior (and the detectors within NSM) to avoid ingesting a chemical specifically associated with danger.

Flavell says it’s likely that some of the fundamental mechanisms highlighted in the new paper will inform studies of similar mechanisms in other animals.

“We developed a way of identifying these pathways by studying this organism that specializes in bacterial detection and displays robust responses,” Flavell explains. “But there’s no reason these pathways should be limited to C. elegans. The molecular players we identified are found in many species, including mammals.”

In addition to Estrem and Flavell, the paper’s other authors are Malvika Dua, Colby Fees, Greg Hoeprich, Matthew Au, Bruce Goode, and Lingyi Deng.

The National Institutes of Health, the McKnight Foundation, the Alfred P. Sloan Foundation, the Howard Hughes Medical Institute, and The Freedom Together Foundation provided support for the study.