Research Highlights

Our pick of the latest scientific literature

  • Volume 547
  • Issue 7664
MRSA was observed shortly after the drug that gives it its name.

SPL

Evolution

Methicillin resistance was out there before methicillin

Study of superbug samples sheds light on evolution of drug resistance.

The MRSA bacterium that plagues many hospitals had evolved resistance to the antibiotic methicillin before the drug was even discovered.

Matthew Holden at the University of St Andrews in Scotland and his colleagues collected 209 samples of methicillin-resistant Staphylococcus aureus (MRSA) that were isolated in the United Kingdom and Denmark between 1960 and 1989. By sequencing their genomes and determining the rate at which the different strains had evolved, the researchers determined that the bacteria had acquired the methicillin-resistance gene, mecA, in the mid-1940s. Methicillin did not enter widespread clinical use in Britain until 1959, and resistance was first observed in 1960.

The researchers suggest that the use of earlier drugs such as penicillin, which are part of the same broad class of beta-lactam antibiotics, inadvertently selected for S. aureus strains carrying the mecA gene.

Energy

Molecular pulleys ease the strain for lithium-ion batteries

Stretchy polymers could point the way forward for silicon anodes.

Silicon is a promising material for use as anodes in lithium-ion batteries, because it can take up more lithium per unit of volume or mass than can graphite, the material currently used.

This means that it could store more energy. But engineers have struggled to make usable silicon anodes because they expand in volume by up to 400% during charging and quickly disintegrate.

Researchers have now devised a molecular-scale ‘pulley system’ that could solve the problem. Jang Wook Choi and his colleagues at the Korea Advanced Institute of Science and Technology in Daejeon attached polysaccharide rings to silicon crystals and then threaded strings of polyethylene glycol polymer through these rings.

As the silicon expanded and contracted, the strings stretched and slid through the rings, keeping the material intact.

Cancer

An Achilles heel for kidney cancer

Switching off gene slows tumour growth in mice.

A new target for fighting the most common form of kidney cancer has been identified.

Clear cell renal cell carcinoma is associated with mutations in the tumour suppressor gene VHL, which increase levels of the HIF transcription factor protein. HIF activates genes including several that help to remove methyl-group chemical tags from the histone proteins around which DNA coils.

William Kaelin of Harvard Medical School in Boston, Massachusetts, and his colleagues found that this increase in HIF makes tumour cells more dependent on a counterbalancing gene called EZH1, which transfers methyl groups to histones.

Inactivating EZH1 using CRISPR gene editing or a drug preferentially inhibited the growth of cancer cells that lacked VHL. Drugs targeting EZH1 also slowed the growth of clear cell renal carcinomas in mice. EZH1 could be a target for drugs against this form of kidney cancer, the authors say.

Genetics

Gene drives face an uphill struggle

CRISPR-based technologies could fight spread of diseases, if they can overcome resistance.

Genetic tools that aim to spread specific mutations through wild populations to eliminate diseases will need to overcome numerous sources of resistance. If successful, these ‘gene drives’ could end the transmission of illnesses such as malaria, by using CRISPR–Cas9 gene editing to propagate mutations that suppress mosquito populations or block them from carrying the disease.

A team led by Jackson Champer and Philipp Messer at Cornell University in Ithaca, New York, engineered fruit flies (Drosophila melanogaster) with gene drives that used CRISPR to spread a gene for a red fluorescent protein through lab populations. The drives did this by copying themselves to unedited chromosomes during the formation of germ cells, which give rise to sperm and eggs.

However, the CRISPR system occasionally introduced random mutations that made the chromosome resistant to the gene drive. This occurred both during the formation of germ cells and in the embryo, after fertilization. Different strains of flies developed resistance at vastly different rates. Efforts to deploy gene drives in the wild will need to overcome these hurdles, the authors say.

Researchers dug into the sand to uncover evidence of prehistoric tsunamis.

Researchers dug into the sand to uncover evidence of prehistoric tsunamis. Earth Observatory of Singapore

Ocean sciences

A history of Sumatran tsunamis

Cave sediments show big Indonesian tsunamis happen sporadically.

Tsunamis have hammered the western coast of Sumatra, Indonesia, at least 11 times in the past 7,400 years. That’s not counting the 2004 tsunami that killed more than a quarter of a million people.

Charles Rubin, of the Earth Observatory of Singapore, and his colleagues dug into sediments at the bottom of a coastal cave in Sumatra. They found 11 layers of sand, each washed in by a prehistoric tsunami between 7,400 and 2,900 years ago. Records from more recent events may have been destroyed by water entering the cave in subsequent tsunamis, the authors suggest. The cave contains the best-preserved and most complete history of Indonesian tsunamis for this period.

On average, the events happened about every 450 years — although at one stage, none occurred for more than 2,000 years, after which four happened in the span of a century. This irregular pattern could complicate efforts to prepare for the next big one.

Particle physics

The proton just got lighter

Most precise measurement so far of tiny particle’s mass could help explain antimatter conundrum.

The proton is slightly lighter than previously believed, according to the most accurate measurement so far of this particle’s mass.

Protons weigh slightly more than one atomic mass unit (defined as one-twelfth the mass of a carbon-12 atom) and scientists have been steadily refining the precision of this measurement. Florian Köhler-Langes of the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, and his colleagues measured the mass of a proton relative to that of a carbon-12 nucleus, by comparing how the particles moved inside an electromagnetic trap.

They achieved a precision of 32 parts per trillion in their result, making it about three times better than previous attempts. They found the proton to be about 296 parts per trillion lighter than the current accepted value. Researchers want to compare this measurement with the mass of antiprotons. Any resulting discrepancy between the proton and its antiparticle could help to explain why the Universe contains vastly more matter than antimatter.

Plastic items are much more likely to end up discarded than recycled.

Plastic items are much more likely to end up discarded than recycled. Fred Dufour/AFP/Getty

Environmental sciences

The fate of all of our plastics

Huge scale of human plastic production and discarding revealed.

Humans have manufactured about 8.3 billion tonnes of plastic since mass production began in the 1950s, and 60% of all the plastic ever produced now lies discarded in landfill or as litter.

Roland Geyer at the University of California, Santa Barbara, and his colleagues collected plastic-production data from industry and market-research companies. They combined that information with data on the typical useful lifetime of different plastics, ranging from less than a year for packaging to more than 30 years for construction materials.

The authors estimate that 2.5 billion tonnes of plastics are currently in use worldwide, with the largest market being packaging. Of the 8.3 billion tonnes of plastic produced so far, 6.3 billion tonnes is estimated to have become waste by 2015. Of this, 12% was incinerated and 79% accumulated in landfill sites and the natural environment. Just 9% was recycled.

Many of the fish caught around the world are obtained by trawling the sea floor.

Many of the fish caught around the world are obtained by trawling the sea floor. Kambou Sia/AFP/Getty

Ecology

Sea beds take years to recover from bottom trawling

Huge impact of fishing on invertebrate life quantified.

Trawling the bottom of the ocean can strip up to 41% of invertebrate life from the sea bed, and ocean floors can take more than six years to recover.

Globally, around one-quarter of wild-caught seafood comes from bottom trawling, but the impact of this type of fishing has been unclear.

Jan Geert Hiddink at Bangor University, UK, and his colleagues combined data from 70 studies around the world to model the ecosystem damage of trawling. ‘Otter trawls’, which use heavy boards at the front of nets to plough up the sea bed, were the least harmful, removing around 6% of bottom-dwelling invertebrates. Most damaging were hydraulic dredges, which use high-pressure water to stir up animals for harvesting. These removed 41% of invertebrates. Recovery from losing 50% of an area’s biomass to trawling takes between 1.9 and 6.4 years, according to the authors’ model. Combining the model with maps of trawling frequency will allow the assessment of this type of fishing on unprecedented scales, say the authors.

Genomics

How people came to Madagascar

Study of 2,704 genomes investigates origins of island’s modern residents.

A study of the genomes of 2,704 people across 257 Madagascan villages suggests the island was settled more recently and more rapidly than previously thought, casting doubt on a conventional theory of the native people’s ancestry.

Thierry Letellier at the University of Toulouse in France and his colleagues found that people from Indonesia probably arrived on the southeastern coast between 3,000 and 2,000 years ago. Ancestors from Africa living in the north then travelled south about 1,500 years ago, and the populations interbred. The authors found stronger paternal genetic lineages from African ancestry, whereas maternal lineages were predominantly from Southeast Asia in all regions of Madagascar except the north, suggesting that journeys south were made primarily by men.

These findings challenge a popular idea that modern Malagasy people descended from a theoretical ancient population referred to as the Vazimba. A genetic signature called M23 that is found only in humans from Madagascar probably arose around 1,200 years ago, say the authors, rather than coming from a group of Vazimba settlers.

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