Research Highlights

Our pick of the latest scientific literature

  • Volume 545
  • Issue 7654
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The varroa mite (shown sitting on honeybee hairs in this scanning electron microscope image) is honeybee parasite that can spread viruses. Erbe & Pooley/USDA/ARS/EMU

Agriculture

Beekeeping practices boost parasite risk

Suppressing natural honeybee behaviours in crowded apiaries could enhance the spread of mites.

Varroa mites (Varroa destructor) spread viruses, feed on honeybee larvae and could be contributing to widespread losses of bee colonies. Beekeepers try to control the pests using chemicals; but in an 11-month study of 120 commercial colonies, Gloria DeGrandi-Hoffman at the US Department of Agriculture in Tucson, Arizona, and her colleagues revealed that 55% of treated hives were still lost. 

A model that simulated varroa populations and bee interactions showed that natural swarming, which is suppressed in domesticated bees, keeps varroa populations down. That’s because swarming carries mites away from hives and reduces the number of bee larvae produced, shrinking the mites’ food supply. Furthermore, infected forager bees that raid other hives can quickly spread the mites when hives are close together. 

The authors think varroa might be impossible to control unless changes are made to the way bees are kept.

Materials science

3D-printed device makes clean steam

The evaporator uses solar energy to efficiently purify water.

Most evaporators that use solar heating rely on lenses or mirrors to concentrate sunlight, which makes it difficult to stop heat being lost to the environment and reduces efficiency. Liangbing Hu and his colleagues at the University of Maryland in College Park built a device using a 3D-printed material made of carbon nanotubes and graphene oxide, which absorbs 97% of incoming sunlight and rapidly warms up. This layer sits on a box with no bottom, which was 3D-printed using porous graphene oxide and nanostructured cellulose. When placed in shallow water, the walls of the box wick water to the top layer, where it is heated and escapes as steam.

The device used 85.6% of the absorbed energy to generate steam, which is one of the highest efficiencies achieved by evaporators. The approach could help to ease shortages in areas where water has to be sterilized or desalinated, the authors say.

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This planet-like object (artist's representation), called SIMP0136, was thought to be a brown dwarf. NASA/JPL, slightly modified by Jonathan Gagné

Astronomy and astrophysics

A celestial case of mistaken identity

From failed star to lonely planet, an interstellar oddity gets a second look.

A nearby celestial object that astronomers thought was a failed star turns out to be a planet-like object that does not orbit a star.

The object, dubbed SIMP0136, is slightly more than 6 parsecs from Earth, in the constellation Carina. It was previously pegged as one of the closest known brown dwarfs, which are bigger than planets but too small to burn hydrogen in their cores as stars do.

But SIMP0136’s mass is only about 13 times that of Jupiter — putting it on the boundary between planets and brown dwarfs, according to Jonathan Gagné at the Carnegie Institution of Washington in Washington, DC and his colleagues, who observed the object using the Keck II telescope in Hawaii. 

Only a few free-floating planets have ever been found, so SIMP0136 offers astronomers a rare opportunity to explore an exoplanet atmosphere without interference from the light of a nearby star.

Chemical biology

Small molecule shuttles iron into cells

A natural compound boosts absorption of the nutrient in animals with iron-transport deficiencies.

A small molecule can function like a protein transporter by moving iron into cells. This suggests a possible way of treating diseases such as anaemia that are caused by dysfunctional or missing iron-transport proteins.

Martin Burke at the University of Illinois at Urbana–Champaign and his colleagues tested the ability of iron-binding small molecules to move the metal into yeast cells that are missing an iron-transporting complex. They homed in on hinokitiol, a compound made by the Taiwan hinoki tree (Chamaecyparis taiwanensis). The molecule restored iron transport in human and mouse cells deficient in any one of three different transporter proteins. In rodents with these deficiencies, hinokitiol increased the absorption of iron into the gut roughly fourfold, and in one animal model returned it to normal levels.

The small molecule seems to collaborate with proteins in the cell to usher in iron after levels have built up outside the cell.

Engineering

A filter-free way to purify water

Bubbling carbon dioxide in water can remove suspended particles.

Harnessing carbon dioxide to purify water uses less energy than typical filtration methods. 

Water is generally purified by being pumped across expensive membranes, which uses a lot of energy. Howard Stone at Princeton University in New Jersey and his colleagues have devised a way to eliminate the need for filters. They suspended 500-nanometre-wide polystyrene particles in water and exposed one side of the mixture to CO2. The gas dissolved in the water, generating an ion gradient that drove negatively charged polystyrene particles to one side and positively charged ones to the other so that they could be removed from the water.

Many microbes are charged, so this method could be used to remove bacteria and viruses without chlorination or ultraviolet treatment, the authors say.

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Enterococcus faecalis survives well in hospitals and can easily fend off antibiotics. Eye of Science/Science Photo Library

Microbiology

Why some drug-resistant bacteria thrive in hospitals

Adaptations to terrestrial life could be the key to their success. 

Two members of a group of gut microbes have evolved multi-drug resistance to become leading hospital-adapted pathogens. The bacteria, called enterococci, are thought to have diverged from an aquatic ancestor around 425 million years ago, when the first animals moved onto land. 

To find out why some enterococci have adapted so well to hospital life, Michael Gilmore at the Massachusetts Eye and Ear Infirmary in Boston, Ashlee Earl at the Broad Institute in Cambridge, Massachusetts, and their colleagues sequenced the genomes and studied the characteristics of 24 species of Enterococcus and 5 species from closely related genera. 

The team found that the enterococci share a core set of 1,037 genes. These encode enzymes that, among other things, produce a hardened cell wall that protects the bacteria from drying and from other harsh conditions on land. The adaptations could have enabled the microbes to flourish in hospitals and develop drug resistance, the authors suggest. 

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Hot springs formed these rock deposits, called geyserite, 3.5 billion years ago. T. Djokic et al./Nat. Commun. (CC BY 4.0)

Geology

Microbes liked it hot 3.5 billion years ago

Ancient rocks suggest that some of Earth’s earliest life may have emerged near hot springs.

The 3.48-billion-year-old Dresser Formation contains ancient evidence for life on the planet. A team led by Tara Djokic at the University of New South Wales in Kensington, Australia, analysed deposits from the formation and identified a type of rock called geyserite that is produced by terrestrial hot springs. The researchers also found signatures of microbial life, including layered rock structures called stromatolites, near the geyserite deposits. The study extends the geological record of life on land by nearly 600 million years.

The search for ancient life on Mars should focus on such environments, the authors suggest.

Immunology

Male hormones curb allergies in mice

The finding could explain why asthma affects more women than men.

Male sex hormones inhibit the development of key immune cells involved in asthma and other allergic responses.

Jean‑Charles Guéry at the French National Institute of Health and Medical Research in Toulouse, Cyril Seillet at the Walter and Elisa Hall Institute of Medical Research in Parkville, Australia, and their colleagues found that male mice have fewer of the cells – called group 2 innate lymphoid cells – and are less likely than females to develop airway inflammation when exposed to an environmental allergen. Castrating the males eliminated these differences. 

The progenitors of these immune cells have receptors that bind male sex hormones. Biochemical signalling through the receptor inhibited the cells’ development.

Biotechnology

Ancient protein resurrected in bacteria

Engineering an ancestral protein into E. coli makes it virus-resistant.

Viruses often commandeer their hosts’ proteins to turn infected cells into virus factories. Researchers have tried inactivating these proteins to boost virus resistance in plants, but this can harm the hosts. Jose Sanchez-Ruiz and his colleagues at the University of Granada in Spain have developed another way of doing this, using Escherichia coli, which can be infected by a bacteriophage — a bacterial virus — called T7. 

The authors focused on one of the bacterium’s thioredoxin genes, which T7 hijacks and uses to replicate during infection. They replaced this gene with one of several ancestral versions that encode forms of the protein that T7 has not encountered before. The team found that a bacterial thioredoxin from about 2.5 billion years ago conferred T7 resistance with minimal effect on the bacterium’s growth. 

This method could be used to make crops resistant to viruses, the authors say.  

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