What builds up can also tear down, a new study of bacteria suggests.
Bacteria build biofilms, communities of the microorganisms encased in a protective goo that shields the microbes from antibiotics and immune system attacks. But the very enzymes bacteria use to construct that shield can also destroy some of its molecules and strip away the protection, researchers report May 20 in Science Advances.
“We’re weaponizing the bacteria against themselves,” says P. Lynne Howell, a structural microbiologist at the Hospital for Sick Children in Toronto. Howell and colleagues studied Pseudomonas aeruginosa bacteria, which can cause pneumonia and other infections and is particularly problematic for people with the lung disease cystic fibrosis. The researchers discovered that two enzymes, PelAh and PslGh, which the bacteria use to build two different sugar polymers, can degrade those same polymers. That delete function, supplied by parts of the enzymes known as glycoside hydrolase domains, normally helps correct mistakes or prevents buildup of the sugar chains inside bacterial cells, Howell says.
In laboratory tests, synthetic versions of the glycoside hydrolase domains applied to P. aeruginosa cultures stopped the bacteria from forming new biofilms and melted existing ones. Stripping away sugar polymers did not kill the bacteria but did make them more vulnerable to antibiotics and immune cells. Human lung cells grown in dishes containing the enzymes suffered no harm, suggesting the enzymes wouldn’t damage human tissues.
Animal tests are needed to determine whether the enzymes are safe and can fight biofilm infections in the body, Howell says. Similar enzymes from other bacteria and fungi may also fight biofilm infections caused by those organisms, she says.
Giant pandas have better ears than people — and polar bears. Pandas can hear surprisingly high frequencies, conservation biologist Megan Owen of the San Diego Zoo and colleagues report in the April Global Ecology and Conservation.
The scientists played a range of tones for five zoo pandas trained to nose a target in response to sound. Training, which took three to six months for each animal, demanded serious focus and patience, says Owen, who called the effort “a lot to ask of a bear.”
Both males and females heard into the range of a “silent” ultrasonic dog whistle. Polar bears, the only other bears scientists have tested, are less sensitive to sounds at or above 14 kilohertz. Researchers still don’t know why pandas have ultrasonic hearing. The bears are a vocal bunch, but their chirps and other calls have never been recorded at ultrasonic levels, Owen says. Great hearing may be a holdover from the bears’ ancient past.
At night, a river of stars cuts through the dense darkness of space. These celestial bodies form our galaxy’s core and their soft glow earned our galaxy the moniker “Milky Way.” But for more than a third of Earth’s population, the glare of artificial lights conceals this cosmic wonder from view, researchers report June 10 in Science Advances. Nearly 80 percent of North Americans and 60 percent of Europeans can no longer see the galactic core at night, the researchers estimate.
Using a combination of satellite measurements and on-the-ground observations, the researchers assembled the first global atlas of artificial sky luminance, recording light pollution from everything from streetlamps to spotlights. Nearly four in five people worldwide live under light-polluted skies, the atlas reveals. Singapore boasts the brightest nights, the team found, with skies so luminous that no one living there can fully adapt to night vision. Nights are darkest in Chad, the Central African Republic and Madagascar, where more than three-quarters of inhabitants can gaze up at the stars under pristine viewing conditions. Bright nights aren’t just an eyesore for stargazers. Artificial lights can disrupt wildlife by, for example, confounding sex-seeking fireflies (SN Online: 8/12/15) and misguiding moths (SN: 6/13/15, p. 9).
I am on a mission. I want everyone to appreciate and understand science — even those who assume (often based on the way they were taught in school) that they don’t like it. Science is important, and frequently amazing. In this issue alone, you can read about the solar-powered spacecraft that, after a five-year journey, will soon arrive at Jupiter to discover what lurks beneath the planet’s blanket of haze and clouds. As NASA’s Juno spacecraft settles into a cloud-skimming series of orbits around the gas giant, it will probe what makes up the planet, its origins and the nature of its core. Learn about efforts to developvaccines for mosquito-ferried scourges , from Zika to dengue. And read about the latest volley in the confounding search for the cause of Alzheimer’s and ancient cave circles built by Neandertals. Luckily, I work for an organization with a mission aligned with my own. And Society for Science & the Public just got a big boost in its efforts to sow understanding and appreciation of science. On May 26, the Society announced a new sponsor of its flagship competition, the Science Talent Search. Like the science fair I wrote about in the last issue (SN: 6/11/16, p. 2), STS offers young scientists a national stage on which they can shine. Regeneron Pharmaceuticals Inc. of Tarrytown, N.Y., has stepped in to replace Intel, STS sponsor since 1998. (Founded by the Society in 1942, STS was originally sponsored by Westinghouse.)
Regeneron has also upped the game, pledging $100 million over 10 years and increasing the value of the scholarships and other awards to $3.1 million annually. The top student winner will now get $250,000, enough for a full-ride at many universities. “We are over the moon,” Maya Ajmera, CEO and president of the Society and publisher of Science News, told the Washington Post. “Regeneron is truly helping the Society scale its work in an unprecedented way,” she says. Regeneron, founded in 1988, developed the cholesterol-fighting drug Praulent that went on sale last year and Eylea, used to treat vision diseases such as wet macular degeneration, among other products. Regeneron’s chief scientific officer George Yancopoulos was a top-10 finalist in STS in 1976. Yancopoulos (a former trustee of the Society) and his fellow STS alum Leonard Schleifer, Regeneron CEO and president, now want to give back. “The Westinghouse was a game changer for me as a high school student,” Yancopoulos says. “It truly set me on the path I am on today. I want to be able to grow that ability to motivate the best and the brightest to pursue careers in science.”
Notably, the biotech firm will dedicate $30 million of the total to expand the Society’s efforts in outreach and equity, designed to encourage more young people to engage in original research. In addition to better supporting educators using research-based approaches, the new funds will increase grants to teachers working with underserved students. It will also grow the Science News in High Schools program, sending the magazine to 4,000 more high schools and, I hope, inspiring students to make discoveries of their own.
We are also expanding efforts to get Science News to you. Look for our updated iPad app in July and, coming soon, apps for Android tablets, Kindle Fire and smartphones.
Two newly discovered Triceratops relatives sported some peculiar headgear.
Researchers uncovered skull fragments of Machairoceratops cronusi in 77-million-year-old mudstone from the Wahweap Formation in southern Utah. Unlike other horned dinosaurs, the roughly 8-meter-long M. cronusi had two grooved horns with spatula-like tips bowed forward from the back of its neck shield. The grooves’ function baffles researchers.
A different research team found a younger cousin of M. cronusi in Montana’s Judith River Formation. Spiclypeus shipporum lived about 76 million years ago and had distinct brow horns that protruded sideways from its skull along with unusual spikes on its neck shield — some pointing outward, others bent forward. S. shipporum’s distinct horns and spikes may have allowed individuals of the species to recognize one another, says Jordan Mallon, a paleobiologist involved in the research at the Canadian Museum of Nature in Ottawa.
The new finds add to the diversity among the herbivorous horned dinosaurs that roamed North America during the Late Cretaceous period. “We thought we knew most things [about horned dinosaurs],” says Eric Lund, a paleontologist at Ohio University in Athens who analyzed M. cronusi. “But we’ve just scratched the surface.”
Papers detailing the new species were published May 18 in PLOS ONE.
ORLANDO, Fla. — Weight gain may depend on how an individual’s genes react to certain diets, a new study in mice suggests.
Four strains of mice fared differently on four different diets, William Barrington of North Carolina State University in Raleigh reported July 15 at the Allied Genetics Conference.
One strain, the A/J mouse, was nearly impervious to dietary changes. Those mice didn’t gain much weight or have changes in insulin or cholesterol no matter what they ate: a fat-and-carbohydrate-laden Western diet, traditional Mediterranean or Japanese diet (usually considered healthy) or very low-carbohydrate, fat-rich fare known as the ketogenic diet. In contrast, NOD/ShiLtJ mice gained weight on all but the Japanese diet. Those mice’s blood sugar shot up — a hallmark of diabetes — on a Mediterranean diet, but decreased on the Japanese diet.
FVB/NJ mice didn’t get fat on the Western diet, but became obese and developed high cholesterol and other health problems on the ketogenic diet. The opposite was true for C57BL/6J mice. They became obese and developed cholesterol and other problems linked to heart disease and diabetes in people on the Western diet, but not on the ketogenic diet. They also fattened up on the Mediterranean diet.
The results indicate that “there’s no universally healthy diet,” Barrington said. The findings echo results of a human study in which blood sugar rose in some people after eating some foods, even when the same food had no effect on other people (SN: 1/9/16, p. 8). Such individual reactions to food suggest that diets should be personalized.
Barrington and colleagues are working to find the genes that control the mouse strains’ varying responses to what they eat. There is still no way to predict how people will fare on a given diet, he said.
For the first time in the United States, free-flying genetically modified mosquitoes have federal approval to take wing in Florida. But when, and if, that will happen is still up in the air. Local officials will make the final decision — possibly not until after the November elections.
The World Health Organization has recognized these mosquitoes as possible tools for fighting the spread of mosquito-borne Zika virus. But the U.S. Food and Drug Administration’s decision, announced August 5, covers only a specific, preliminary test release of GM mosquitoes on Key Haven in the Florida Keys, where no locally transmitted Zika cases have been reported. This trial of OX513A mosquitoes, genetically engineered by the British company Oxitec, “would be unlikely to result in adverse effects on the environment or human health,” the FDA ruled. If Key West commissioners approve it, the trial would release abundant GM male Aedes aegypti species carrying a gene that will cause their offspring to die. In tests in Brazil, Panama and the Cayman Islands, months of releasing these mosquitoes has reduced the wild populations of Ae. aegypti mosquitoes by 90 percent or more. As a result, a Brazil neighborhood has seen mosquito-borne dengue cases plummet (SNOnline: 7/15/16).
To see whether OX513A could work in the United States, too, the test release would now need approval from the Florida Keys Mosquito Control District Board of Commissioners. Opponents of GM organisms have protested the idea, so the five commissioners have arranged for a nonbinding referendum question to appear on the November ballot. Commissioners plan to wait until the community has weighed in before making their final decision, says mosquito control district spokeswoman Beth Ranson.
If the mosquito plan gets a thumbs up, Oxitec could release mosquitoes in December, said Hadyn Parry, the company’s chief executive officer. Monitoring and testing could take six months and results would go back to the FDA with an application to allow the mosquitoes to be released commercially — and more broadly — in the United States for mosquito control.
As Zika rages in Puerto Rico, and with Miami reporting the first locally mosquito-transmitted cases on the U.S. mainland, debate over the controversial mosquito has taken on new urgency. Tom Frieden, director of the U.S. Centers for Disease Control and Prevention, has noted that efforts to eradicate mosquitoes in an area in Miami have fallen short (SNOnline: 8/1/16).
Ae. aegypti mosquitoes resist many pesticides, bite during the day, love human houses, and can breed in plant saucers and other small pools of water. Virtually a domestic animal, this species bites people almost exclusively. It’s suspected to be the main spreader of Zika virus, and also does a fine job of infecting people with dengue, chikungunya and yellow fever viruses. Oxitec GM mosquitoes, developed in 2002, would target Floridian pests via a new twist in the decades-old strategy of male sterilization. Mid-20th century entomologists sterilized screwworms by irradiating them and releasing the decoy males in overwhelming clouds. So many wild females mated with these sterile males that eventually the gruesome screwworm pests of livestock disappeared from the United States.
OX513A, with their mix of old-fashioned strategy and newfangled genetic tinkering, has kicked up anti-GMO feeling, even though it’s not the first U.S. approval of testing a GM insect in pest control. That honor goes to pink bollworms in the Southwest in 2009, though their release passed largely unnoticed outside the pest-control community. But when the FDA released a favorable draft opinion in March, saying the GM-mosquito test would probably have “no significant impact” on people or the environment, more than 2,000 people typed comments on the public FDA site. Many were vehemently opposed to the plan, peppering their comments with multiple exclamation points and the occasional “OMG!!!”
Some commenters worried about blood contact from the bite of a GM organism, possible allergies should someone accidentally swallow one and unknown consequences to the environment.
Oxitec posted explanations responding to those fears: Almost all mosquitoes released would be males, which don’t bite; males will die three or four days after release; their offspring are engineered to die without unnatural amounts of tetracycline — a lab-provided supplement — in their diets. Angry public comments, however, largely dismissed these reassurances as corporate-funded research.
Another commenter wondered whether a successful test, driving down the Ae. aegypti population on the Keys, could make room for some other insect menace. That’s a reasonable question, says Phil Lounibos of the University of Florida in Vero Beach. He has studied competition between Ae. aegypti and the relentlessly biting Asian tiger mosquito, Aedes albopictus. These tiger mosquitoes were once rare on the Keys, but he has found that they can take over from Ae. aegypti, in part by sexual deception. Tigers that mate with Ae. aegypti females render the females sterile and have thus conquered other parts of Florida. Even though Ae. aegypti is recognized as a more potent vector for human disease, the tigers can carry many of the same viruses (including Zika), Lounibos warns (SNOnline: 5/16/16).
As far as ecological concerns go, entomologist Bruce Tabashnik of the University of Arizona in Tucson, has no problem with eradicating Ae. aegypti from the Florida Keys or anywhere else in the Americas. “It’s an invasive species,” he says. “There are no ecological ethics violated.”
Tabashnik was part of the research team monitoring the first GM insect release in the United States: sterile male pink bollworms. Males of this invasive pest species that prey on cotton in the Southwest were sterilized by radiation. However, Oxitec had inserted a gene that made them fluoresce red so monitors could tell the friendlies from the wild targets. Tabashnik recalls no particular public outcry over the experiment. It took place in a sparsely populated area and, instead of mosquitoes, involved a kind of moth only a cotton farmer could hate.
So far outrage, or even interest, in other tweaked pest-control animals seems minimal compared with GM-mosquito fever. A proposed test of Oxitec’s GM diamondback moth in New York has inspired fewer comments. Tests of a non-GM but still tinkered-with mosquito — Ae. albopictus developed to carry Wolbachia bacteria that interfere with mating — were first approved in 2012 for release in American Samoa. Later tests have released these bacteria-carrying mosquitoes in California and other sites in the mainland United States.
WASHINGTON — When bacteria lose genes needed to make enzymes for important chemical reactions, defeat isn’t inevitable. Sometimes other enzymes will take on new roles to patch together a work-around chain of reactions that does the job, biologist Shelley Copley reported August 4 at the 2nd American Society for Microbiology Conference on Experimental Microbial Evolution.
Bacteria that can adapt in this way are more likely to survive when living conditions change, passing along these new tricks to their descendants. So studying these biochemical gymnastics is helping scientists to understand how evolution works on a molecular level. Working with different strains of Escherichia coli bacteria, Copley and colleagues deleted genes responsible for making crucial enzymes. The team then watched the microbes replicate for many generations to see how they worked around those limitations.
Most enzymes are highly specialized: They only work well to speed up one type of reaction, the way a key fits only one lock. But some enzymes are more like master keys — they can boost multiple reactions, though they tend to specialize in one. These so-called “promiscuous” enzymes can switch away from their specialty if conditions change.
Copley’s team found that new enzymes would sub in to replace the missing ones. For instance, E. coli missing an enzyme needed to make vitamin B6 synthesized the vitamin using a different set of enzymes. But surprisingly, the promiscuous enzymes didn’t end up directly triggering the same reaction as the enzymes they replaced. Instead, the replacement enzymes cobbled together a different (often longer) work-around series of reactions that ultimately achieved the same function.
“We were rerouting metabolism,” said Copley, of the University of Colorado Boulder.
By modifying the bacteria’s genes and forcing the microbes to survive with a more limited chemical toolkit, Copley’s work gives a more detailed look at the biochemistry underlying evolution, says biologist Gavin Sherlock of Stanford University, who was not involved in the research. Betul Kacar, a synthetic biologist at Harvard University, says promiscuity could also be a window into the past, giving hints about enzymes’ previous roles earlier in evolutionary history. The role that an enzyme jumps in to play in a pinch could have once been its main job. “Trying to understand how novel pathways arise, what kind of mechanistic underlying forces shape those trajectories, is quite essential,” she says.
Bacteria can piece together all sorts of alternative routes in response to missing enzymes, depending on specific environmental conditions, Copley said. The ones that are most successful are more efficient —they have fewer steps, or they yield more of the desired reaction product.
Even if you’ve never lived in rattlesnake territory, you know what the sound of a snake’s rattle means: Beware! A shake of its rattle is an effective way for a snake to communicate to a potential predator that an attack could result in a venomous bite.
For more than a century, scientists have posited how that rattle might have evolved. The rattle is composed of segments of keratin (the same stuff that makes up human hair), and specialized muscles in a snake’s tail vibrate those segments rapidly to create the rattling sound. The rattlesnake’s rattle is a trait that evolved only once in the past and is now found in only two closely related genera of snakes that live in North and South America. But plenty of other species of snakes also vibrate their tails as a warning to potential predators.
Bradley Allf and colleagues at the University of North Carolina in Chapel Hill think that the tail vibration and the evolution of the rattle might be connected. They gathered 155 snakes of 56 species — 38 species from the Viperidae family, which includes rattlesnakes, and 18 species from the largest snake family, Colubridae — from museums, zoos and private collectors. Working with captive snakes let them control conditions, such as temperature, that can affect tail vibration. With each snake, one of the researchers tried to get it to behave defensively by waving a stuffed animal in front of it. The team videotaped the snakes as they vibrated their tails, or not.
The researchers plotted the snakes’ tail vibration duration and rate against how closely related a species was to rattlesnakes. One group of snakes that lives in the Americas was taken out of the analysis because its tail vibrations were so similar to those of rattlesnakes; it appears that these species are mimicking the dangerous snakes that live near them (not a bad strategy for survival). Among the rest of the snakes analyzed, those that were more closely related had tail behavior that was more similar to that of rattlesnakes.
“Our results suggest that tail vibration by rattleless ancestors of rattlesnakes may have served as the signal precursor to rattlesnake rattling behavior,” the researchers write in the October issue of the American Naturalist. “If ancestral tail vibration was a reliable cue to predators that a bite was imminent, then this behavior could have become elaborated as a defensive signal.”
Allf and his colleagues propose a couple of ways that this could have happened. Perhaps snakes that made noise with their tails were better at startling predators, and this may have prompted such noise-making tail features to spread and eventually become refined into what is now a rattle. Or maybe snakes that shook their tails longer and faster developed calluses of keratin. If these calluses provided better warning, that may have somehow evolved into a rattle.
“Thus, the rattlesnake rattle might have evolved via elaboration of a simple behavior,” they conclude.
The first time Jessica Cantlon met Kumang at the Seneca Park Zoo, the matriarch orangutan regurgitated her previous meal right into Cantlon’s face. “I was retching,” Cantlon recalls. “It was so gross.” But Cantlon was there to kick off a series of behavioral experiments, and her students, who would be working with Kumang regularly, were watching. “Does anyone have any towels?” she remembers asking, knowing she had to keep her cool.
Cantlon’s deliberate nature and whatever-it-takes attitude have served her well. As a cognitive neuroscientist at the University of Rochester in New York, she investigates numerical thinking with some of the most unpredictable and often difficult study subjects: nonhuman primates, including orangutans, baboons and rhesus macaques, and — most remarkably — children as young as age 3. Both groups participate in cognitive tests that require them, for example, to track relative quantities as researchers sequentially add items to cups and to distinguish between quantities of assorted dots on touch screens. The kids also go into the functional MRI scanner where, in a feat impressive to parents everywhere, they lie completely still for 20 to 30 minutes so Cantlon and colleagues can get pictures of their brains. “She takes steps carefully, and she thinks very hard about where she is going,” says Daniel Ansari, a developmental cognitive neuroscientist at the University of Western Ontario in London, Canada, who is familiar with Cantlon’s work. “She goes for the big questions and big methodological challenges.”
The central question in Cantlon’s research is: How do humans understand numbers and where does that understanding come from? Sub-questions include: What are the most primitive mathematical concepts? What concepts do humans and other primates share? Are these shared concepts the foundation for fancier forms of mathematical reasoning? In addressing these questions, Cantlon draws on a wide range of methods. “Very few people can combine work on cognitive skills — studies from the point of view of behavior — with imaging work in very young children, and very few people do that same combination in nonhuman primates,” says Elissa Newport, who chaired the brain and cognitive sciences department at Rochester for more than a decade and now leads the Center for Brain Plasticity and Recovery at Georgetown University.
As a graduate student, Cantlon determined that neuroimaging studies would add an independent source of data to the cognitive questions under exploration in Elizabeth Brannon’s lab at Duke University. So she identified collaborators and taught herself functional MRI. “By the time she graduated, she had something like four dissertations’ worth of work,” says Brannon, now of the University of Pennsylvania.
In the years since, Cantlon has identified a type of “protocounting” in baboons; they can keep tabs on approximate quantities of peanuts as researchers increase those quantities (SN Online: 5/17/15). In her most attention-grabbing work, Cantlon studied activity in the brains of children while they watched Sesame Street clips that dealt with number concepts — an unexpected success that proved everyday, relatively unaltered stimuli can yield meaningful data. An ongoing study in Cantlon’s lab seeks to find out how monkeys, U.S. kids and adults, and the Tsimané people of Bolivia, who have little formal education, distinguish between quantities. Do they determine the number of dots presented on the computer screen or do they rely on a proxy such as the total area covered by the dots? The work explores how the brain understands everyday concepts, but it could also inform strategies in math education. “If we understand the fundamental nature of the human brain and mind, that might give us a better insight into how to communicate number concepts to kids,” Cantlon says.
Growing up outside of Chicago, Cantlon enjoyed digging deep into a topic and becoming an expert. She and a friend turned themselves into ice skating superfans one summer, reading up on the Olympic skaters and checking videos out of the local library. In another project, Cantlon decided to learn everything possible about the price of gold. When she moved to a school where she could no longer take Latin, she taught and tested herself. Despite the fact that neither of her parents went to college, no one ever questioned that Cantlon would go. She studied anthropology as an undergraduate at Indiana University in Bloomington. “I was interested in the question of where we come from,” Cantlon says. “I was interested in studying people.” During college, she went on an archaeological dig in Belize and studied lemurs in Madagascar. For a year after graduation, she observed mountain gorillas in Rwanda, detailing their behavior every 10 minutes. “What they were thinking was something that was constantly on my mind,” she says. “‘How are we similar? Are you thinking what I’m thinking?’” Though she might have succeeded in any number of careers, she wanted exploration to be a big part of her life: “I don’t think doing a less exotic type of work would have been as satisfying.”
Today, Cantlon, who at age 40 recently earned tenure, doesn’t spend much time in the field. And even in the lab, she leaves much of the data collection to her graduate students and research assistants. “At this point, we are a well-oiled system,” she says, referring to the brain scan studies on kids. To make the kids comfortable, Cantlon’s team does trial runs in a mock scanner, describing it as a spaceship and providing “walkie-talkies” for any necessary communication. To keep them interested, the researchers treat it as a team activity and offer a ton of positive reinforcement, with prizes including Lego sets and a volcano-making kit. The kids receive pictures of their brains, which typically interest the parents most. The older of Cantlon’s two daughters, a 5-year-old extrovert named Cloe, has participated in behavioral tests and will no doubt be excited for her first brain scan.
The Sesame Street study was in part inspired by a paper by Uri Hasson, a neuroscientist at Princeton University who imaged the brains of volunteers while they watched The Good, the Bad and the Ugly. To better understand brain development, Cantlon wanted to see how brain activity compared in kids and adults exposed to math in a natural way. Of particular interest was a region called the intraparietal sulcus, or IPS, thought to play a role in symbolic number processing. The results, reported in PLOS Biology in 2013, showed that kids with IPS activity more closely resembling adults’ activity performed better on mathematical aptitude tests.
“It was the clearest, cleanest — did not have to come out this way — result,” Cantlon says.
Cantlon is notable for her diverse set of tools, says Steve Piantadosi, a computational neuroscientist and colleague at Rochester. “But she has something which is even more powerful than that. If you have different hypotheses and you want to come up with the perfect experiment that distinguishes them, that is something she is very good at thinking about. She is a great combination of critical and creative.”
To add another methodological approach, Cantlon next plans to collaborate with Piantadosi to develop computational models that explain the operations the brain performs as it counts or compares quantities. She would also like to add data analyses from wild primates into the mix. When researchers talk about the evolution of a primitive number sense, they often speak about foraging activity — identifying areas of the forest with more food, for example. But Cantlon wonders whether social interactions also require some basic understanding of quantities.
As for a recent question from a colleague about what risky project she’ll pursue now that she has tenure, Cantlon says nothing in particular comes to mind: “I feel like we’ve been doing the crazy things all along.”
