Waterlily beetles (Galerucella nymphaeae) literally fly across water, high speed videography and a bit of mathematical modeling reveals.

The beetles have a combination of hydrophobic hairs that line their legs and hydrophilic claws that grip the surface of water without getting too wet. Prior to “take off,” the insects lift their middle pair of legs. Then, the insects beat their wings extremely fast and fly horizontally across a pool of water. It looks a lot like water-skiing.
In lab tests, waterlily beetles reached 0.5 meters per second — without an active brake system. Surface tension keeps the insects afloat, they found. The insects create ripples in the water, which generates drag at speeds greater than 0.23 meters per second (more drag than when the beetles just fly through air). Thus, for these beetles, skiing across a pond at breakneck speeds costs a lot of energy and requires greater wing thrust than normal flying. However, this mode of getting around could be more advantageous for foraging and help them avoid underwater predators like fish, the researchers speculate March 2 in the Journal of Experimental Biology.

After the Exxon Valdez dumped more than 10 million gallons of oil into the Gulf of Alaska, hairdresser Phil McCrory got an idea.

He gathered up human hair from his salon, stuffed it into a pair of pantyhose and dunked the bundle into a solution of motor oil and water. The hair sopped up the oil — a discovery that has since inspired environmentalists to create “hair blankets” to clean up oil spills.
It’s not the most bizarre use of hair that Kurt Stenn describes in his new book, Hair: A Human History, or even the most surprising. From the felted wool covers of tennis balls to the horse-tail hair of a violin’s bow, Stenn, a former dermatologist and hair follicle scientist, digs up the myriad ways that hair has threaded its way into humans’ lives — and history.

A thriving wool trade starting in the 13th century, for example, helped some Italians amass enough wealth to later support famous artists of the Renaissance, including Michelangelo. And in 17th century Europe, beaver fur was so in demand (felted hats were a must for stylish gentlemen) that traders hunted beavers to near extinction.

Stenn jams an encyclopedia’s worth of material into a mere 256 pages, all the while shedding facts like a golden retriever sheds fur. But the book has more than just history. Stenn details the molecular biology of hair, those packed piles of cells that push out of nearly every square inch of human skin (except for the palms, soles and a few other areas). Hair conditioner, he explains, works by leaving positively charged molecules on strands, so that they repel each other rather than tangling together.

Stenn roots his story in science, discussing evolution, development and disease, among other topics. (The book could give readers a sure win for any hair category on Jeopardy!.) But Hair shines when Stenn steps out of the lab and into the world. He visits a wigmaker’s workshop in London, tours a modern barbering institute in Pennsylvania and learns about synthetic fibers at the laboratories of a Tokyo-based wig company.

These interludes are subtle highlights in a densely woven tale. But throughout, Stenn manages to convey a sense of wonder for a seemingly mundane material so tough, so strong and so versatile that it can be used for virtually anything — even mopping oil from the sea.

Ancient Assyrians sent their dead to the afterlife with fearsome companions: turtles. Excavations of a burial pit in southeastern Turkey revealed skeletons of a woman and a child, plus 21 turtles, a team led by archaeologist Rémi Berthon of France’s National Museum of Natural History reports in the February Antiquity.

The burial is part of an Assyrian site called Kavuşan Höyük that dates to between 700 and 300 B.C. The turtle bonanza included shells from one spur-thighed tortoise (Testudo graeca) and three Middle Eastern terrapins (Mauremys caspica), plus bones from 17 Euphrates soft-shelled turtles (Rafetus euphraticus). Butchering marks on the R. euphraticus bones indicate that the turtles may have been eaten in a funerary feast, Berthon and his colleagues write.
Back then, turtles were not a regular meal in Mesopotamia. Turtle bones, however, were thought to ward off evil. The abundance of R. euphraticus turtles, a notoriously aggressive species, in this burial pit suggests the deceased had high social status.

To ancient Assyrians, these ferocious reptiles probably represented eternal life and served as psychopomps — mythical guides to the afterlife, the team writes.

Editor’s Note: This story was updated on 4/15/16 to note that turtles were a rare part of the Mesopotamian diet.

Earth sciences reporter Thomas Sumner recalls seeing the documentary film An Inconvenient Truth when he was in high school. The climate science presented in the movie didn’t surprise him too much — a science-minded student, he had already read about many of the issues. But, he says, the film started a broader dialog about global warming.
“People started caring,” he says, noting that he remembers his own family talking about it (and not always harmoniously) at the time. Revisiting the dramatic predictions made in the film proved an interesting journey for Sumner.
“The main criticism I heard was that the film had watered down the science,” he says. Climate science is amazingly complex, and so is modeling effects of change — from how much sea level might rise to how a warming climate could alter hurricane patterns. Even more striking to Sumner were the sheer number of uncertainties that remain. Those uncertainties are not about whether the climate is changing, but about the details of what such changes will mean for the oceans, the atmosphere and the living things on land — and when the various dominoes might fall. Telling the future is hard, especially about interrelated complex systems, but as Sumner reveals in his story, scientists have made steady progress in the last decade.

Another interesting point is the documentary’s (and Al Gore’s) role in politicizing climate science, which is fair to assume was one of the aims. “Gore was polarizing,” Sumner says. “He created a conversation about global warming, but he also cemented it as a political issue.”

Teeth and gums are neither political nor talked much about. But, as contributing correspondent Laura Beil reports, scientists studying a possible role for gum disease in what ails the body must contend with a slew of uncertainties, not unlike those faced by climate scientists. The bacteria that cause gum disease, some studies find, can travel to the arteries, heart, brain and other sites where they can cause havoc. Not all studies agree, and proving the oral bacteria–disease link beyond a doubt may not yet be within scientists’ grasp. But the fix is relatively simple, even if avoided by many: frequent flossing and regular visits to the dentist.

Keeping things simple was the underlying goal of the team of scientists attempting to build, from scratch, a synthetic organism with the least possible number of genes, as Tina Hesman Saey reports. After many tries, the effort succeeded, but not without first humbling the researchers involved. In the initial attempts, their computer-designed minimal genomes didn’t take. What ultimately worked was putting back some of the unknowns — genes with no known cellular job to do. Only then did the DNA inserted into the shell of a microbial cell yield a synthetic microbe capable of growing and reproducing.

Telling a good story about complex science, whether in a film or in a report on the latest research, requires some simplification. But sometimes the most interesting part lies in the uncertainty.

Our galaxy is teeming with planets. Over the last 25 years, astronomers have cataloged about 2,000 worlds in 1,300 systems scattered around our stellar neighborhood. While most of these exoplanets look nothing like Earth (and in some cases, like nothing that orbits our sun), the bonanza of alien worlds implies a tantalizing possibility: There is a lot of real estate out there suitable for life.

We haven’t explored every corner of our solar system. Life might be lurking beneath the surface of some icy satellites or in the soil of Mars. For such locales, we could conceivably visit and look for anything wriggling or replicating. But we can’t travel (yet) to worlds orbiting remote suns dozens of light-years away. An advanced alien civilization might transmit detectable radio signals, but primitive life would not be able to announce its presence to the cosmos.
At least not intentionally.
On Earth, life alters the atmosphere. If plants and critters weren’t around to keep churning out oxygen and methane, those gases would quickly vanish. Water, carbon dioxide, methane, oxygen and ozone are examples of “biosignatures,” key markers of a planet crawling with life as we know it. Setting aside questions about how recognizable alien life might be, detecting biosignatures in the atmosphere of an exoplanet would give astronomers the first strong clue that we are not alone.
Biosignatures aren’t proof of thriving ecosystems. Ultraviolet light from a planet’s sun can zap water molecules and create a stockpile of oxygen; seawater filtering through rocks can produce methane. “We’ll never be able to say 100 percent that a planet has life,” says Sarah Rugheimer, an astrophysicist at the University of St. Andrews in Scotland. But astronomers hope that, given enough information about an exoplanet and the star it orbits, they can build a case for a world where sunlight and geology aren’t enough to explain its chemistry — one where life is a viable possibility. Finding a planet similar to Earth is probably still decades away, but thanks to a couple of upcoming telescopes, astronomers might be on the verge of spying on habitable worlds around nearby stars.

NASA’s Transiting Exoplanet Survey Satellite, or TESS, will launch in 2017 on a quest to detect many of the exoplanets that orbit the stars closest to us. One year later, the James Webb Space Telescope will launch and peek inside some of these newfound atmospheres. With their powers combined, TESS and James Webb could identify nearby planets that are good candidates for life. These worlds will probably be quite different from Earth — they’ll be a bit larger and orbit faint, red suns — but some researchers hope that a few will offer hints of alien biology.
Eyes on the sky
Over the next decade, several telescopes will join existing observatories in the hunt for exoplanets and hints of alien life.

Exoplanets don’t give up their secrets easily; they are distant, tiny and snuggled up to blazing stars. With some exceptions, current telescopes can’t directly see exoplanets, so astronomers use other means to infer their existence. In rare cases, a remote solar system is oriented so that its planets pass between their sun and Earth, an event known as a transit. During a transit, the star temporarily dims as a planet blocks some of its light.

Transits are powerful tools; not only can they help reveal a planet’s density — a way to distinguish gas planets from solid ones — but they also can allow astronomers to inventory the molecules floating in an exoplanet’s atmosphere. During a transit, molecules in the planet’s atmosphere absorb certain wavelengths of the star’s light, leaving a chemical fingerprint. By deciphering that fingerprint, researchers can deduce the chemical makeup of an alien world.

Pushing Hubble
Astronomers so far have used the transit technique primarily with space-based telescopes such as the Hubble Space Telescope to investigate the atmospheres of more than 50 exoplanets, most of them worlds the size of Jupiter and Neptune (SN: 11/15/14, p. 4). The puffy atmospheres of giant planets are easier to detect than the relatively slim atmospheres of small rocky worlds. As tools have improved, researchers have started to check out super-Earths, planets that are smaller than Neptune but larger than ours. Though no such planets exist in our solar system, they appear to be one of the most common types in the galaxy.

Only three super-Earths have come under telescope scrutiny so far: GJ 1214b, HD 97658b and 55 Cancri e. These worlds are nothing like Earth. Two of them orbit dim, red suns, all of them whip around their stars in a few days (or even hours) and none are in the coveted habitable zone — the region around a star where a planet’s temperatures are just right for liquid water. Around GJ 1214b and HD 97658b, astronomers found no signs of molecules absorbing starlight, leading researchers to conclude that both worlds are blanketed in clouds or haze (SN Online: 1/2/14).

In February, researchers reported signs of hydrogen cyanide on 55 Cancri e. If confirmed, it would be the first detection of any molecule in the atmosphere of a super-Earth. “These are very challenging measurements, at the limit of [the Hubble Space Telescope’s] capabilities,” cautions Heather Knutson, an astrophysicist at Caltech. “We’re still learning about the performance of the telescope at this level of precision.”

Astronomers will undoubtedly try to squeeze more information out of similar worlds. But, says Kevin France, an astrophysicist at the University of Colorado Boulder, “we’ve pushed Hubble about as far as we can.” And Hubble won’t be around forever (SN: 4/18/15, p. 18). To continue sniffing around in exoplanet atmospheres, researchers are looking toward Hubble’s successor, the James Webb Space Telescope.

James Webb “is going to be a revolution in astronomy,” says Jonathan Lunine, an astrophysicist at Cornell University. The infrared observatory boasts a mirror 2.7 times as wide as Hubble’s. James Webb will seek out the first generation of stars, track how galaxies grow and — most relevant to the search for life — poke around in planetary atmospheres.
Analyzing the atmospheres of planets the size of Neptune and Jupiter should be a breeze for James Webb. These large planets block enough light to make transits readily detectable, and the fluffy atmospheres are easier to measure. Super-Earths, which are smaller with thin atmospheres, are more challenging, but James Webb should be able to investigate a few. Although replicas of Earth are beyond even James Webb’s capabilities, there will be plenty for the observatory to do. “Even if we can’t get biosignatures on planets the size of Earth, we’re going to find out so much about the nature of exoplanets,” Lunine says. “It’s going to open up a huge number of doors.”

The trouble with an Earth-like world is that it doesn’t transit often and both the planet and its atmosphere are tiny. It’s the same kind of problem an alien group would experience trying to detect us. When viewed from afar, Earth blocks less than 0.01 percent of the sun’s light, and only a few percent of that is due to the atmosphere. To an alien astronomer, Earth crosses the sun once a year for, at most, 13 hours. And that’s assuming the aliens live in the right part of the galaxy to witness an Earth transit. Telescopes operated by the bulk of the Milky Way’s citizens will never line up with both the sun and Earth.

Focus on M dwarfs
The odds of finding life improve if astronomers focus their efforts on M dwarfs, which make up about three-quarters of the stars in the galaxy. The dim red orbs are small, so a transiting planet blocks a relatively large fraction of the star’s light, making transits easier to detect. Habitable worlds also transit more frequently. To sustain liquid water, a planet must huddle close to one of these cool stars to stay warm. An orbit in the habitable zone of an M dwarf is much shorter than a comparable trip around the sun. Rather than wait for a year between transits, astronomers might have to wait for only a few weeks or months. Plus, a planet on a cozy orbit is more forgiving when it comes to getting the viewing geometry just right to see a transit.
There are potential downsides to M dwarfs. Most of the light they radiate is infrared, so photosynthesis on orbiting planets would be very different compared with photosynthesis on Earth. There’s no guarantee that biosignatures from vegetation that thrives on infrared light would look anything like those from local varieties. Many M dwarfs also emit occasional blasts of ultraviolet radiation — blasts made even more dangerous because any habitable planet sits close to the star. Habitable worlds need to be so close, in fact, that the star’s gravity might prevent the planet from rotating, which could give rise to extreme climate differences between day and night. Recent research, though, indicates that none of these issues are necessarily deal breakers (SN: 2/7/15, p. 7). “There’s no reason why a planet around an M star couldn’t be like Earth,” says Lisa Kaltenegger, an astrophysicist at Cornell.

James Webb should be able to poke around in the atmospheres of a few habitable super-Earths around M dwarfs, though it’s going to need some targets first (SN: 5/17/14, p. 6). NASA’s premier planet hunter, the Kepler space telescope, (SN: 12/27/14, p. 20) found 1,039 exoplanets during its four-year primary mission, with 4,706 additional candidates awaiting confirmation. But most of Kepler’s finds are too distant for James Webb. That’s where TESS comes in. It will catalog all the short-period transiting worlds around the sun’s nearest neighbors. “Those are the ones that astronomers even decades from now are going to want to focus on,” says George Ricker, an MIT astrophysicist and principal investigator for the TESS mission.

Unlike Kepler, which gazed in one direction at 150,000 stars, TESS will spend two years monitoring 200,000 stars all around the sky. To cover that much ground, TESS will stare at one spot for about 27 days before moving onto a new patch. That’s not great for finding Earth twins on year-long orbits, but it’s good for finding worlds in the habitable zones of M dwarfs.

Based on Kepler’s results, astrophysicist Peter Sullivan, then at MIT, and colleagues calculated in 2015 that TESS should discover about 1,700 exoplanets. Of these, more than 500 could be less than twice the size of Earth, of which about 50 would lie in the habitable zones of their host stars. But picking biosignatures, or any signatures, out of those atmospheres is going to be difficult. Estimates vary, but James Webb will need roughly 200 hours to study one super-Earth around a nearby M dwarf, and those hours count only when the planet is passing in front of its star.

There’s a debate happening right now over how hard to chase that dream, Caltech’s Knutson says. Given its sluggish pace, James Webb might get to look at only a couple of habitable super-Earths. Astronomers could lavish large amounts of time on one or two systems that might not even pan out. Or they could focus telescope resources on Neptunes, Jupiters or hot super-Earths, where researchers can amass a lot of other data about a wide variety of worlds. While James Webb might get lucky and spy some biosignatures, the dream of finding another planet like Earth will probably have to wait a few decades for a larger observatory to come along.
Snapping a pic
The transit technique is powerful but inefficient. From our vantage point, most planets don’t transit their suns, and those that do transit only once every orbit.

“To really give us the best probability of detecting life, we need to build a telescope that can do direct detection,” Rugheimer says. Direct detection requires snapping a picture of an exoplanet and looking for biosignatures such as oxygen and methane imprinted on light reflecting off its surface. Since this technique doesn’t require alignments between planets and suns, it can, in principle, work for any world around any star. But to catch an Earth 2.0, astronomers are going to need a bigger telescope.

Consider again those aliens who are looking for us. They would struggle to see Earth even if they set up camp 4.2 light-years away at the star next door, Proxima Centauri (an M dwarf, by the way). It’s like trying to see the head of a quilting pin 28 meters to the right of a basketball while standing about 7,500 kilo-meters away — roughly the distance from Honolulu to Pittsburgh. And the basketball is 10 billion times as bright as the pin.

No observatories come close to being able to capture an image of an Earth-like planet around a sunlike star. But astronomers are thinking about what it would take. One idea is to put a gigantic mirror in space equipped with a device that can block the light of the star, such as the High-Definition Space Telescope proposed by the Association of Universities for Research in Astronomy. To see a few dozen Earth twins and characterize their atmospheres, that telescope would need a mirror 12 meters across. That’s bigger than any optical telescope currently on the ground and has 25 times the light-collecting area of Hubble.

Such an observatory “would be a huge undertaking relative to what we’ve done in space before,” Lunine says. “But relative to other programs this country has undertaken, it’s not.”
One of the keys to success with the high-definition telescope is a coronagraph, a disk that blocks the light from any star the telescope points at. Many telescopes already use coronagraphs, especially spacecraft designed to look at the sun. James Webb will be outfitted with a coronagraph, though not one designed to search for other Earths.

The downside to a coronagraph is that it requires exceptional control of light that enters the telescope, which complicates the design. Other proposals to detect Earth-like planets, such as the NASA-commissioned Exo-S concept, use a starshade, a separate spacecraft shaped, appropriately, like the petals of a sunflower. The starshade flies tens of thousands of kilometers away from the telescope and maintains perfect alignment to prevent starlight from hitting the mirror (SN: 7/12/14, p. 11).

Since a starshade is free-floating and does all the lightsuppression work, it should be able to partner up with any telescope, even a relatively small one already in use. But no one has attempted formation flying in space at this scale. And every time astronomers want to look at a new star, the starshade would have to move around the telescope to maintain alignment, which could take days or weeks. All that movement will require fuel, which limits how many stars astronomers can search.
Today these missions and others like them exist only in papers and PowerPoint slides posted online. The concepts, the fruits of a community-wide brainstorming session on how to allocate funding in the 2030s and beyond, will require massive financial and logistical resources, but some astronomers think it will be worth it once TESS and James Webb can point to where the nearest habitable locales might be. “Once we know where the potential habitable worlds are in our sky, I hope that will change a lot of people’s curiosity,” Kaltenegger says. “I would want to know if there are other habitable worlds. I wouldn’t want to just guess.”

Everyone agrees that finding a world teeming with life elsewhere in the galaxy is going to be exceptionally difficult. “Maybe nature needs to be on our side,” says Mark Clampin, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “But it won’t stop people from trying very hard. And we’ll probably make a lot of discoveries along the way.”

CERN’s Large Hadron Collider is in standby mode after a 66-kilovolt/18-kilovolt electrical transformer suffered a short circuit April 29 at 5:30 a.m. Central European Time. The culprit: A small wild animal, believed to be a weasel, gnawing on a power cable.

“The concerned part of the LHC stopped immediately and safely, though some connections were slightly damaged due to an electrical arc,” Arnaud Marsollier, who leads CERN’s press office, wrote in an e-mail to Science News.

Sadly, the weasel did not survive the event, but the LHC should be back online soon. “It may take a few days to repair but such events happened a few times in the past and are part of the life of such a large installation,” Marsollier writes. The power outage comes just as the LHC is preparing to resume collecting data.

This isn’t the the first time an odd event has stalled operations at the particle collider outside Geneva on the Swiss-French border. In 2009, a piece of bread (supposedly a baguette dropped by a bird or from an airplane) interrupted a power installation for an LHC cooling unit.

A popular type of heartburn medicine could hasten wear and tear of blood vessels.

Proton pump inhibitors, or PPIs, gunk up cells that typically line the veins and arteries like a slick coat of Teflon, researchers report May 10 in Circulation Research. Excess cellular junk ages the cells, which could make blood vessels work less smoothly.

The results, though controversial, are the first inkling of evidence that might explain why PPIs have recently been linked to so many different health problems, from heart attacks to dementia.
“The authors present a compelling story,” says Ziyad Al-Aly, a nephrologist at the Veterans Affairs Saint Louis Health Care System in Missouri. It begins to outline how using PPIs could spell trouble later on, he says. But Al-Aly notes that the study has one big limitation: It was done in cells, not people.

Gastroenterologist Ian Forgacs from King’s College Hospital in London agrees. Drawing conclusions about humans from cells grown in the lab requires “a huge leap of faith,” he says. So far, scientists have found only correlations between PPIs and their alleged side effects. “We need to know whether these drugs really do cause dementia and coronary disease and renal disease,” he says.

In the last few decades, proton pump inhibitors have emerged as a kind of wonder drug for heartburn. The drugs switch off molecular machines that pump acid into the stomach. So less acid surges up to burn the esophagus.

In 2012, nearly 8 percent of U.S. adults were taking prescription PPIs, according to a survey published last year in JAMA. (Some PPIs are also available over-the-counter.) Many people use PPIs for longer than they’re supposed to, says study coauthor John Cooke, a cardiologist at Houston Methodist Research Institute in Texas. “These are very powerful drugs­ — they’re not Tums,” he says. “They have side effects.”

Several of these side effects are still under debate. And if PPIs do increase the risk of dementia, say, or kidney disease, no one knows how. So Cooke and colleagues explored what chronic exposure to the drugs, which travel through the bloodstream, does to cells lining the blood vessels.
Human cells treated with a PPI called esomeprazole (sold as Nexium) seemed to age faster than untreated cells, the researchers found. The cells lost their youthful shape and instead “looked kind of like a fried egg,” Cooke says. They also lost the ability to split into new cells, among other signs of aging.

Cooke traced the rapid aging to mishaps in acid-filled cellular chambers called lysosomes. These chambers act as tiny garbage disposals; they get rid of junk like broken-down proteins. But PPIs, which work so well at shutting down acid production in the stomach, also seemed to shut down the acidic garbage disposals, too, the researchers found. That caused proteins to pile up, forming “little heaps of rubbish,” Cooke says.

Mucking with blood vessels’ lining could trigger all sorts of problems. For instance, instead of gliding easily through, platelets and white blood cells could get hung up, sticking to vessel walls like Velcro. “That’s how hardening of the arteries starts,” Cooke says.

The next step is to see if similar damage occurs in people. Doctors and regulatory agencies should take a second look at the widespread use of PPIs, too, Cooke says. “There’s enough data now that we have to be very cautious in our use of these agents.”

But some researchers think PPIs are getting a bum rap. “Everybody and their mother now want to hammer PPIs,” says gastroenterologist David Metz of the University of Pennsylvania. “It’s unfortunate because they’re spectacular drugs and they save people’s lives.”

The real question, Al-Aly says, is whether the benefits outweigh the risks.

In the scorching heat of the Kalahari Desert, some birds still manage to keep their cool.

Thermal imaging reveals that the southern yellow-billed hornbill (Tockus leucomelas) vents heat from its beak, a phenomenon previously observed in toco toucans (Ramphastos toco). A team of South African researchers snapped infrared photos of 18 hornbills on a farm in the southern edge of the desert at temperatures from 15° to 45° Celsius.

When air temperatures hit 30.7° Celsius, the difference between beak surface temperature and air temperature spikes — indicating the birds were actively radiating heat through their beaks. At most, the birds lost about 25.1 watts per square meter through their beaks. Hornbills probably manage this cool trick by dilating the blood vessels to increase flow in their uninsulated beaks, the team writes May 18 in PLOS ONE.

Toucans lose about 60 percent of their total heat loss through their beaks, but hornbills only shed up to 20 percent of their heat loss through this method. The researchers chalk that difference up to larger beak-to-body-size in toucans.

A last-ditch weapon against drug-resistant bacteria has met its match in Pennsylvania.

A 49-year-old woman has tested positive for a strain of Escherichia coli resistant to the antibiotic colistin, researchers report May 26 in Antimicrobial Agents and Chemotherapy.

It’s the first time in the United States that scientists have found bacteria carrying a gene for colistin resistance known as mrc-1, write study coauthor Patrick McGann of Walter Reed Army Institute of Research in Silver Spring, Md., and colleagues.
But perhaps even more alarming is that the gene rides on a transferable loop of DNA called a plasmid.

“That means we now see a possibility of spread,” says physician and clinical microbiologist Robert Skov. And not just from mother cell to daughter cell, he says, but to neighboring strains of bacteria, too.

Bacteria carry most of their genetic information in a tangle of DNA contained in chromosomes inside the cell. But tiny loops of DNA called plasmids hang around outside of the tangle. These loops carry extra information that bacteria can use, like how to protect themselves from antibiotics. Bacteria can swap plasmids like trading cards, effectively spreading instructions for antibiotic resistance.

In December, Skov and colleagues discovered a Danish patient carrying bacteria with mcr-1 plasmid DNA, like the woman in Pennsylvania. And in November of 2015, researchers reported something similar in China.

Until then, all known colistin resistance was due to tweaks in chromosomal DNA (which, unlike plasmid DNA, isn’t easily spread among bacteria), says Skov, of the Statens Serum Institut in Copenhagen, who was not involved with the new work.

Colistin, a 50-year-old drug that doctors largely stopped prescribing in the 1970s because of its side effects, has made a comeback in the last five to 10 years. It’s used when other antibiotics fail; it’s a treatment option for people infected with multidrug-resistant bacteria. Now, with colistin-resistant bacteria, Skov says, antibiotic treatment options are becoming more and more limited.

The problem, scientists have been pointing out for years, is that people are taking antibiotics too frequently. More use means more opportunity for bacteria to develop resistance.

Still, even with colistin-resistant bacteria emerging all over the world, Skov says he doesn’t expect thousands of people to become infected.

“The scenario now is that once in a while, we’ll see a patient carrying bacteria that we don’t have any good antibiotics left for.” But that, he adds “is dreadful enough.”

Improvements in a technique for making “three-parent babies” could reduce the risk of passing on faulty mitochondria, the energy-producing organelles in cells.

Less than 2 percent of mitochondria were defective in most human embryos created from this refined “pronuclear transplantation” procedure, researchers report online June 8 in Nature.

Pronuclear transplantation is one of two ways to transfer nuclear DNA from a mother’s egg that has faulty mitochondria to a donor egg with healthy mitochondria. After fertilization, the mother’s and father’s chromosomes don’t merge but are encased in separate membranes inside the mother’s egg. In pronuclear transplantation, researchers remove both of these DNA packages, known as pronuclei, and inject them into an empty donor egg.
Any resulting children would inherit DNA from three parents: most from their mother and father, with a small amount of mitochondrial DNA from the egg donor. DNA transplant techniques may prevent mothers from passing mitochondrial diseases to their children. Such diseases, which result from mutations in mitochondrial DNA, particularly affect energy-hungry organs, including the brain and muscles.

Last month, researchers reported that even small amounts of defective mitochondria carried into the healthy egg might propagate and negate the effect of the therapy (SN Online: 5/19/16).

In the new study, flash-freezing the mother’s egg, removing pronuclei soon after they form (about eight hours after fertilization) and other refinements greatly reduced the amount of defective mitochondria transplanted into donor eggs. Of embryos created, 79 percent carried less than 2 percent of defective mitochondria, report reproductive biologist Mary Herbert of the Wellcome Trust Centre for Mitochondrial Research in Newcastle upon Tyne, England, and colleagues.

That decrease in defective mitochondria doesn’t eliminate the risk of disease resurgence, but greatly reduces it, says Herbert. “The focus of our current research is to get that carryover as close to zero as we possibly can.”