30 August 2014 | NewScientist | 17

Yeasts to take on the opium farmers

SEVERE pain? Reach for the yeast. Genetically engineered yeasts can now produce a range of opiates, including morphine. With growing anxieties about supplies of opium poppies, it could be just what the doctor ordered.

Many of the most widely used opiate painkillers can be produced only from opium poppies (Papaver somniferum). Some 50 per cent of the plants for these booming drugs are grown on the Australian island of Tasmania, so poor growing seasons can affect availability.

Christina Smolke of Stanford University in California and her colleagues have been looking at synthesising these complex molecules from simple sugars. In 2008, she genetically engineered yeasts to build an opiate precursor molecule. Now her team has finished the end of the pathway, engineering yeasts to synthesise finished drugs from another type of precursor molecule (Nature Chemical Biology, DOI: 10.1038/nchembio.1613). “This work gets us very close,” says Smolke. All that’s left now, she says, is to combine the two phases in one strain of yeast, and fill in the missing steps.

The approach could free up farmland. Some 280,000 hectares are devoted to poppy fields globally. Yeasts could be grown in fermenters in secure facilities, says Smolke.

To see inside Saturn, watch its rings

EAVESDROPPING on Saturn’s rings is revealing secrets of the gas giant’s vast interior.

Conventional wisdom says that Saturn contains a solid central core surrounded by a roiling gassy-liquid mix of helium and hydrogen. “It’s like a giant lava lamp – a slow boiling motion,” says Jim Fuller of the Kavli Institute for Theoretical Physics in Santa Barbara, California. This flow was thought to keep everything evenly mixed.

But images captured by NASA’s Cassini spacecraft revealed steady vibrations at six different places in

Saturn’s rings. Even though the rings are thousands of kilometres from Saturn’s surface, vibrations in them correspond to the way the planet squishes and contracts.

Now Fuller has run a computer simulation of the vibrating rings. The results suggest that Saturn must have a stable, stratified layer, perhaps of liquid and rock, between the core and roiling exterior (Icarus, doi.org/vbh).

This is the first time a seismological investigation has been conducted on another planet. Future work should reveal more about the structure and evolution of gas giants.

IT’S a selfie that might save your sight. An implanted sensor could help people with glaucoma monitor the pressure in their eyes using a smartphone camera.

Glaucoma is the second-biggest cause of blindness after cataracts. It occurs when fluid builds up in the eye. This raises the pressure, damaging the optic nerve. Accurate pressure readings are crucial for giving the right treatment, but one-off measurements during check-ups produce variable results and can be misleading.

Yossi Mandel at Bar-Ilan University in Ramat Gan, Israel, and his colleagues have developed a pressure sensor which can be inserted into the eye during surgery to provide easy, regular monitoring from home (Nature Medicine, DOI: 10.1038/nm.3621).

A few millimetres in length, the sensor can be embedded into the synthetic lenses used to replace the natural lenses of people with cataracts. It works like a miniature barometer, and contains a fluid column that rises with eye pressure. The level can be read

at any time using a smartphone camera fitted with a special optical adapter. Software then analyses the image and calculates the reading.

“Continuous monitoring is a clear unmet need in glaucoma,” says Francesca Cordeiro, a glaucoma researcher at University College London.

Mandel believes self-monitoring will lead to better treatment of the condition, and could enable people to skip unnecessary appointments when their eye pressures are on target.

Tiny implant turns smartphone into glaucoma monitor

Spiders grow larger as cities swell

AS IF Australia’s spiders weren’t big and scary enough, it turns out denser, busier cities are allowing some of them to grow even bigger. The same thing could be happening the world over.

Elizabeth Lowe at the University of Sydney in New South Wales was surprised at just how large some harmless urban golden orb-weaver spiders (Nephila plumipes) were growing.

Examining more than 200 specimens around Sydney, Lowe and her colleagues found that the more concrete there was and the further they were from bushland, the bigger the spiders tended to be. Lowe says the spiders in bushland north of Sydney had an average mass of 0.5 grams. Those in an inner-city park near Bondi Beach averaged 1.6 grams (PLoS One, doi.org/vbf).

“It’s probably because of the urban heat-island effect and prey availability,” says Lowe. “Most invertebrates will grow to larger sizes if they are warmer. They are very sensitive to temperatures.”

Healthy spider populations in cities should be celebrated, says Lowe: they are mostly harmless to people, they eat pests and they are food for birds.

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