We are losing the war against infectious bacteria. They are becoming increasingly resistant to our antibiotics, and we have few new drugs in the pipeline. Worse still, bacteria can transfer genes between each other with great ease, so if one of them evolves to resist an antibiotic, its neighbours can pick up the same ability. But Matti Jalasvuori from the University of Jyvaskyla doesn’t see this microscopic arms-dealing as a problem. He sees it as a target.
Usually, antibiotic-resistance genes are found on rings of DNA called plasmids, which sit outside a bacterium’s main genome. Bacteria can donate these plasmids to one another, via their version of sex. The plasmids are portable adaptations – by trading them, bacteria can rapidly respond to new threats. But they aren’t without their downsides. Plasmids can sometimes attract viruses.
Bacteriophages (or “phages” for short) are viruses that infect and kill bacteria, and some of them specialise on those that carry plasmids. These bacteria may be able to resist antibiotics, but against the phages, their resistance is futile.
In Australia, the penalty for burglary is several years in prison. But that’s for humans. For the small hive beetle, breaking and entering into the hive of stingless bees carries a far harsher sentence – being mummified alive in a sticky tomb of wax, mud and resin.
It’s difficult for people to change their identities or careers, but it can be done. We don’t have to be stuck with one particular fate; with a bit of effort, we can become different people. The same is true for the cells that we’re made of. They come in different types, from brain cells to skin cells to muscle cells. Stem cells can produce all of these types, but once a cell commit to a particular role, it’s largely stuck there.
But not always. Scientists can convert one type of cell into another with the right cocktail of molecules – a process known as transdifferentiation. It’s a cellular makeover. The hope is that this technique will allow doctors to grow bespoke tissues and organs. If someone suffers from a disease that destroys their nervous system, like Alzheimer’s, you could theoretically take their skin cells, and transform them into a fresh supply of genetically identical neurons.
To do this, you need to work out the right recipe. Many groups are working on this. They’ve managed to change pancreatic cells into liver cells, skin cells into heart cells, and more. But no one has been able to transform other types of cells into human neurons. That is, until now. Zhiping Pang, Nan Yang and Thomas Vierbuchen from Stanford University have identified a quartet of proteins that can change human skin cells into working neurons.
In Alice’s Adventures in Wonderland, the titular heroine quaffs a potion that shrinks her down to the size of a doll, and eats a cake that makes her grow to gigantic proportions. Such magic doesn’t exist outside of Lewis Carroll’s imagination, but there are certainly ways of making people think that they have changed in size.
There’s nowhere in the world that’s better at creating such illusions than the lab of Henrik Ehrsson in Sweden’s Karolinska Institute. In a typical experiment, a volunteer is being stroked while wearing a virtual reality headset. She’s lyng down and looking at her feet, but she doesn’t see them. Instead, the headset shows her the legs of a mannequin lying next to her.
As she watches, Bjorn van der Hoort, one of Ehrsson’s former interns, uses two rods to stroke her leg, and the leg of the mannequin, at the same time. This simple trick creates an overwhelming feeling that the mannequin’s legs are her own. If the legs belong to a Barbie, she feels like she’s the size of a doll. If the legs are huge, she feels like a 13-foot giant.
Daniel Kish has no eyes. He lost them to cancer at just 13 months of age, but you wouldn’t be able to tell from watching him. The 44-year-old happily walks round cities, goes for hikes, rides mountain bikes, plays basketball, and teaches other blind youngsters to do the same. Brian Bushway helps him. Now 28 years old, Bushway lost his vision at 14, when his optic nerves wasted away. But, like Kish, he finds his way around with an ease that belies his disability.
Both Kish and Bushway have learned to use sonar. By making clicks with their tongue and listening to the rebounding echoes, they can “see” the world in sound, in the same way that dolphins and bats can. They are not alone. A small but growing number of people can also “echolocate”. Some develop the skill late in life, like Bushway; others come to it early, like Kish. Some use props like canes to produce the echoes; others, just click with their tongues.
The echoes are loaded with information, not just about the position of objects, but about their distance, size, shape and texture. By working with these remarkable people, scientists have worked out a lot about the scope and limits of their abilities. But until now, no one had looked at how their brains deal with their super-sense.
When the dinosaurs were ruling the land, other giant reptiles dominated the oceans. They included the ichthyosaurs, a group of reptiles that bore a strong resemblance to dolphins. They cut through the prehistoric oceans with streamlined bodies, flat flippers and powerful fluked tails. They gave birth to live young in the water. They snapped at fish and squid with pointed snouts, full of conical teeth.
But one of them was different. Shastasurus is a very different type of ichthyosaur. It has a very small head, a short snout and, most importantly, no teeth at all.
Martin Sander from the University of Bonn thinks that it was the black sheep of the family. It couldn’t have bitten its prey like other ichthyosaurs or modern dolphins. Instead, Sander thinks that it was a suction feeder. By quickly opening its mouth and pulling back its tongue, it created a sudden influx of water that swept its prey into its open jaws. Many whales, including sperm whales and beaked whales, hunt with a similar technique today and they too have greatly reduced teeth.
The competition between cats and dogs often takes amusing turns. Last year, cats seemed to edge ahead in the ‘drinking’ event. Until recently, people thought that both pets drink by using their tongues as simple ladles to lap up liquids. But Pedro Reis and Roman Stocker from MIT found that cats do something very different. Using high-speed video recordings, they showed cats drink by using their tongues to draw columns of water into their open jaws. While dogs supposedly drink by scooping up water in a mundane way, cats were portrayed as masters of physics that “defeat gravity” whenever they drink.
Now, A. W. Crompton and Catherine Musinsky from Harvard University have stepped up to even the score for dogs. Through their own high-speed videos – including X-ray films of drinking dogs – they have found that dogs use the same technique the cats do. It’s a draw.
Several species of these freshwater clams are entirely male. Technically, they’re hermaphrodites because each individual produces both sperm and eggs, but the eggs don’t contribute to the next generation. When they are fertilised by sperm, their own DNA gets ejected and the resulting embryo only contains genes from the sperm. In this way, the clams produce clone “sons” that are genetically identical to them.
Like all species that have abandoned sex, the existence of these clams is a mystery. In the short-term, there are many advantages to ditching sex. An asexual animal can pass all its genes to the next generation without spending any effort on finding a mate. But there are serious drawbacks to this lifestyle.
Many animals, including the majority of reptiles, cannot produce their own body heat. To control their temperature, they have to use their environment. They bask in the sun to heat up and lounge in the shade to cool down. And some of them start before they’ve even hatched.
Wei-Guo Du from the Chinese Academy of Sciences has found that the embryos of soft-shelled turtles “bask” inside their eggs. “People usually think reptilian embryos are immobile,” says Du. After all, their limbs are tiny stumps and they have few places to move to. But that doesn’t stop them. Du found that the embryos can not only move, but they can snuggle up to the warmest side of their eggs.