Research Highlights

Our pick of the latest scientific literature

  • Volume 554
  • Issue 7691
An emulsion

Droplets of an organic molecule can be used to build a polymer to order. Credit: E. Rieger at al./Angew. Chem. Int. Ed.

Chemistry

A shortcut for building a complex molecule

Chemists put carefully crafted mixtures to work to construct specialized polymers.

Sturdy molecular chains called gradient polymers have long proved difficult to synthesize. Now, a team has found a simple way to make them.

Polymers consist of different molecular components strung together randomly or in patterns. In a gradient polymer, the composition gradually transitions along the polymer’s length, from mostly one component to mostly another.

Making gradient polymers is a laborious task. Seeking a fix, a team led by Katharina Landfester and Frederik Wurm at the Max Planck Institute for Polymer Research in Mainz, Germany, sequestered two types of organic molecule in a mixture called an emulsion, in which droplets of one liquid are dispersed throughout another. By exploiting the molecules’ different chemical properties, the researchers were able to dissolve one type in the main liquid and the other in the droplets.

Polymerization began only inside the droplets. As that compound was gradually consumed, the change in concentration pulled ever-greater amounts of the other ingredient into the chains, creating a gradient effect.

This 100-million-year-old arachnid in amber had silk-spinning organs but also a long tail.

This 100-million-year-old arachnid in amber had silk-spinning organs but also a long tail. Credit: D. Huang et al./Nature Ecol. Evol.

Evolution

Eight-legged crawlers spin controversy

Arachnid preserved in ancient amber might be an early spider — or not.

An arachnid found in 100-million-year-old Burmese amber from Myanmar boasts a curious mix of characteristics.

The spider-like creature (Chimerarachne yingi) has a tail-like appendage similar to those of other early arachnids, but also has traits seen in modern spiders, such as multi-segment silk-spinning organs.

Gonzalo Giribet at Harvard University in Cambridge, Massachusetts, Diying Huang at the Chinese Academy of Sciences in Nanjing and their colleagues analysed two fossils of the animal dating to about 100 million years ago. On the basis of the creature’s tail, they conclude that it belongs to the Uraraneida, a group of spider relatives that was thought to have gone extinct around 275 million years ago. But Bo Wang, also at the Chinese Academy of Sciences in Nanjing, and his colleagues examined two other fossils of the species and argue that its advanced silk-spinning apparatus shows it was part of a lineage of tailed spiders that survived until at least 100 million years ago.

Silk-spinning spiders with and without tails co-existed for millennia, the authors agree.

Hubble Telescope images of the Small Magellanic Cloud

The Small Magellanic Cloud is one of the closest galaxies to the Milky Way and is easily seen from the Southern Hemisphere. Credit: NASA/ESA/A. Nota (STScI/ESA)

Astronomy and astrophysics

The galactic smash that birthed a slew of stars

Star clusters in nearby galaxies might have had a violent beginning.

A collision between two nearby galaxies might have triggered a burst of star formation in both around 200 million years ago.

The Small and Large Magellanic Clouds are satellite galaxies of the Milky Way. Theodoros Bitsakis of the National Autonomous University of Mexico in Morelia and his colleagues analysed the star ‘clusters’ of the smaller galaxy, each of which contains hundreds or thousands of stars that were all born at the same time. The researchers found that most clusters in the smaller galaxy formed about 240 million years ago — around the same time as the clusters in the larger galaxy.

Simulations by other teams suggest that the two galaxies slammed into each other just before the star clusters formed. The proposed collision could have triggered the bursts of star formation in both systems, the authors say.

Dividing colorectal cancer cell and bacteria cells

A colon-cancer cell divides into two cells. Credit: Steve Gschmeissner/SPL

Microbiology

Tumours grow where two gut bacteria thrive

Microbes in the intestines of some people and mice make toxins that promote tumours.

Two types of bacteria found in the gut might boost the risk of colon cancer, according to studies in mice and humans.

A dense layer of mucus separates the surface of the colon from the trillions of bacteria that reside in the colon’s interior. Cynthia Sears of Johns Hopkins University in Baltimore, Maryland, and her colleagues studied samples of colon tissue from people with a genetic propensity for developing polyps — tiny growths on the colon walls. The team found that the polyps often contained patches of mucus that had been invaded by bacteria.

Two species dominated the patches: Escherichia coli and Bacteroides fragilis, each carrying a gene that encodes a cancer-promoting toxin. When the two bacteria were introduced into mice predisposed to cancer, the mice developed tumours faster than control animals implanted with only one of the bacterial strains. They were also more likely to die during the study period.

Norway rats (Rattus norvegicus)

Norway rats reward helpful companions. Credit: Manon Schweinfurth

Animal behaviour

Fair-minded rats pay helpers with food

If you give a rat a treat, it might reciprocate the favour.

‘Rub my back and I’ll give you a sweet’ — even rats engage in this kind of trade, suggesting that cooperation among animals is more widespread than previously thought.

Common rodents called Norway rats (Rattus norvegicus) are known to exchange food with each other, and to exchange grooming sessions, too. But Manon Schweinfurth and Michael Taborsky at the University of Bern wanted to know whether the animals would swap dissimilar resources, such as food in exchange for a bout of grooming.

The researchers paired test rats with partner rats that, as a result of training and experimental prompting, could provide tasty treats, grooming or nothing at all. Test animals were generally eager to groom the partners who had gifted them food, and vice versa. But test animals tended to be stingy with favours towards a partner that had given them nothing.

A boat floating above a coral reef

Din from boats can interfere with the life lessons of fish living on coral reefs. Credit: Daniela Dirscherl/Getty

Ecology

Shh! Fish are learning

Boat noise disrupts memory formation in damselfish — and increases their risk of death as a result.

Sounds from noisy motorboats prevent fish from learning to recognize new predators.

Maud Ferrari at the University of Saskatchewan in Saskatoon, Canada, and her colleagues played recordings of either the natural sounds heard near a coral reef or the sounds of both a reef and a motorized dinghy to juvenile coral-reef damselfish (Pomacentrus amboinensis). At the same time, the researchers exposed the fish to two smells: that of an unfamiliar predator, and alarm odours produced by injured damselfish.

The next day, the team again exposed the fish to the predator’s odour. Fish that had heard only the reef noise responded with anti-predator behaviours, such as a reduction in foraging. But fish exposed to the noisy boat and reef sounds showed no such reaction, behaving the same way as naive fish that had never encountered the predator’s odour. They were also bolder and more active than the reef-noise group when released into a coral reef near Lizard Island in Australia — making them three times less likely to survive their first three days on the reef.

Smoke from wildfires blanketed northern Canada in mid-August 2017.

Smoke from wildfires blanketed northern Canada in mid-August 2017. Credit: NASA Earth Observatory

Atmospheric science

Catastrophic wildfires mimicked volcanic eruption

Smoke from widespread fires reached the stratosphere and travelled the globe.

The smoke from wildfires that ravaged North America in mid-2017 blotted out as much sunlight as a moderate volcanic eruption.

The smoke was particularly thick in August 2017 as fires burned in northwestern Canada and the United States. Laser instruments at the Haute-Provence Observatory near the village of Saint Michel l’Observatoire, France, tracked the layers of smoke particles as they drifted overhead, and the CALIPSO satellite confirmed the measurements from orbit. A team led by Sergey Khaykin at the Institute Pierre-Simon Laplace in Guyancourt, France, studied these data and report that the smoke blocked more sunlight than the 2009 eruption of Russia’s Sarychev Peak. That eruption measured four out of eight on a scale used to rate the explosive power of volcanoes.

Future studies could provide insight into the mechanisms that allowed the smoke to travel long distances in the stratosphere, the authors say.

A tightrope stroll was too much for the neurons that steady this mouse.

A tightrope stroll was too much for the neurons that steady this mouse. Credit: Getty

Neuroscience

The cells that set the body straight

Wobbling mice reveal the brain circuitry behind stability.

Two distinct groups of brain cells help the body to stabilize itself after it is thrown off-balance, according to a study in mice.

Andrew Murray at the Sainsbury Wellcome Centre for Neural Circuits and Behaviour in London, Thomas Jessell at Columbia University in New York and their colleagues trained mice to walk along a balance beam. When the researchers bumped the beam, an animal steadied itself with two distinct motions: it extended one paw to widen its base of support, then stiffened the muscles around its joints.

The team found that each motion is controlled by a separate group of cells in a brain region called the lateral vestibular nucleus (LVN). The first group signals to the muscles involved in paw extension; the second signals to another brain region that activates muscle stiffening.

When the researchers killed LVN neurons with a toxin, the animals could walk normally but could not steady themselves when nudged off-balance.

The Mississippi River winding through marshlands in Minnesota

Marshes and farmland border a stretch of the Mississippi River near its headwaters in Minnesota. Credit: Nathan Benn/Corbis/Getty

Environmental sciences

How Mother Nature cleans dirty water

Wetlands beat pasture land at scrubbing nitrate pollution from rivers.

Wetlands are natural water purifiers on a vast scale, reducing levels of one common pollutant in rivers much more effectively than a gold-standard method.

Many waterways in the US Midwest are awash in harmful fertilizer by-products called nitrates. Wetlands are known to reduce nitrates, but Amy Hansen at the University of Minnesota in Minneapolis and her colleagues wanted to find out how wetlands compare to other measures for controlling nitrates. The team sampled river water at more than 200 sites in the heavily farmed Minnesota River basin and measured the extent of both crops and wetlands in the area.

The team’s calculations showed that wetlands decrease nitrate pollution up to five times more efficiently than the conversion of farmland to pasture — the best land-based method for reducing nitrates.

The authors say that restoring wetlands could lower pollution levels across an entire watershed.

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