On 13 June, 2011, a woman was transferred to the National Institutes of Health Clinical Center with an infection of Klebsiella pneumoniae. This opportunistic bacterium likes to infect people whose immune systems have been previously weakened, and it does well in hospitals. In recent years, it has also evolved resistance to carbapenems – the frontline antibiotics that are usually used to treat it. These resistant strains kill more than half of the people they infect, and the new patient at the NIH hospital was carrying just such a strain.
She was kept to herself, in her own room. Any doctors or visitors had to wear gowns and gloves. The only contacts she had with other patients were two brief stints in an intensive care unit.
The woman eventually recovered and was released on 15 July. But by then, she had already spread her infection to at least three other patients, despite the hospital’s strict precautions. None of them knew it at the time, for K.pneumoniae can silently colonise the guts of its host without causing symptoms for long spans of time.
The second patient was diagnosed with K.pneumoniae on 5 August, and every week after that, a new case popped up. The hospital took extreme measures. All the infected people were kept in a separate part of the hospital, and assigned a dedicated group of staff who didn’t work on any other patients. The outbreak was contained, but not before it had spread to 18 people in total, and killed 6 of them.
How did the bacteria manage to spread so effectively, despite everything that the hospital did to stem its flow? K.pneumoniae’s stealthy nature makes it nigh impossible to work out the path of transmission through normal means. Instead, Evan Snitkin from the National Human Genome Research Institute sequenced the entire genomes of bacteria taken from all the infected patients. His study is the latest in a growing number of efforts to use the power of modern genetic technology to understand the spread and evolution of diseases.
If you only looked at mammals, you could reasonably believe that the chisellers have inherited the earth. Of all the various species of mammals, forty percent are rodents. Rats, mice, squirrels, guinea pigs… all of them have the same modus operandi. They gnaw their way into their food with self-sharpening chisel-like teeth.
Whether tiny gerbil or huge capybara, rodents eat with the same special teeth. The upper and lower jaws each have a single pair of incisors that grow continuously through their lives. The front of each tooth is made from hard enamel, while the back is made of soft dentine. As the rodent gnaws, the incisors scrape at each other, and the dentine wears away faster than the enamel. This creates a permanently sharp edge, useful for cracking into wood, nuts and flesh alike. Once gnawed, the rodent passes its food to the back of their mouths to be chewed by grinding molars.
But on the Indonesian island of Sulawesi, Jacob Esselstyn has discovered a new species of rodent that radically departs from this universal body plan: a “shrew-rat” that he calls Paucidentomys vermidax.Its name –a mash-up of Latin and Greek—gives a clue to its lifestyle. It means “worm-devouring, few-toothed mouse”.
We don’t have enough organs. Due to our ageing population and the rising burden of chronic diseases, the organs of living people are failing. Meanwhile, those of the recently dead continue to be in short supply, despite well-funded initiatives to increase donation. So what can we do?
In a new feature for The Scientist, I explore two very different solutions to the organ shortage: transplanting them from animals, and growing them afresh. Both approaches have been chugging along for many years, and proponents of both think that they’re on the cusp of something big. I go into a fair bit of detail about the history behind both routes, where they are now, and where they might reasonably get to in the future.
This isn’t an easy piece to structure – it’s almost like two mini-features. But I was struck at how people who work on both approaches were drawn into the field by their frustration at being able to save terminally ill patients but just not having the replacement parts to do it. Do have a read. Here’s the first act, to whet your appetite:
For Joseph Vacanti, the quest to build new organs began after watching the death of yet another child. In 1983, the young surgeon was put in charge of a liver transplantation program at Boston Children’s Hospital in Massachusetts. His first operation was a success, but other patients died without ever being touched by a scalpel. “In the mid-80s, kids who were waiting for organs had to wait for a child of the same size to die,” says Vacanti. “Many patients became sicker and sicker before my eyes, and I couldn’t provide them with what they needed. We had the team, the expertise, and the intensive care units. We knew how to do it. But we had to wait.”
On the other side of the Atlantic, David Cooper was having the same problem. Having taken part in the first successful series of heart transplants in the United Kingdom, he had moved to South Africa to run a transplantation program at the University of Cape Town Medical School. At the time, people had a 50/50 chance of surviving such a procedure, but Cooper recalls that most of his patients were killed by a lengthy wait. “We just didn’t have enough donors,” he says.
Today, the organ shortage is an even bigger problem than it was in the 1980s. In the United States alone, more than 114,000 people are on transplant lists, waiting for an act of tragedy or charity. Meanwhile, just 14,000 deceased and living donors give up organs for transplants each year. The supply has stagnated despite well-funded attempts to encourage donations, and demand is growing, especially as the organs of a longer-lived population wear out.
Faced with this common problem, Vacanti and Cooper have championed very different solutions. Cooper thinks that the best hope of providing more organs lies in xenotransplantation—the act of replacing a human organ with an animal one. From his time in Cape Town to his current position at the University of Pittsburgh, he has been trying to solve the many problems that occur when pig organs enter human bodies, from immune rejection to blood clots. Vacanti, now at Massachusetts General Hospital, has instead been developing technology to create genetically tailored organs out of a patient’s own cells, abolishing compatibility issues. “I said to myself: why can’t we just make an organ?” he recalls.
In the race to solve the organ shortage, xenotransplantation is like the slow and steady tortoise, still taking small steps after a long run-up, while organ engineering is more like a sprinting hare, racing towards a still-distant finish line. Most of those betting on the race are backing the hare. Industry support has dried up for xenotransplantation after years of slow progress, leaving public funders to pick up the expensive tab. Stem cells, meanwhile, continue to draw attention and investment. But both fields have made important advances in recent years, and the likely winner of their race—or whether it will result in a draw—is far from clear.
Photo by Socialisbetter
Since as long as I can remember, nature documentaries and textbooks have said that flocking birds and shoaling fish gather in large coordinated groups to protect themselves from predators. That explanation makes complete sense. After all, many eyes can spot danger more easily, and many bodies can confuse the senses of hunters. But common sense often leads us astray in biology, and very few people have checked to see if collective motion does offer safety from predators.
Christos Ioannou is one of the first. By allowing a predatory fish to hunt virtual prey, whose movements he could precisely control, Ioannou showed that coordinated groups are, indeed, less likely to be attacked. So far, so obvious, but Ioannou’s results have a fascinating implication: predators can trigger the evolution of collective movements, even if their prey can’t see them. While we often think of flocking and shoaling as a response to a hunter’s advances, that response doesn’t have to be a deliberate one. Threatened prey could evolve to move as one even without any knowledge of the threat they face.
None of our machines can do what a cuttlefish or octopus can do with its skin: change its pattern, colour, and texture to perfectly blend into its surroundings, in matter of milliseconds. Take a look at this classic video of an octopus revealing itself.
But Stephen Morin from Harvard University has been trying to duplicate this natural quick-change ability with a soft-bodied, colour-changing robot. For the moment, it comes nowhere near its natural counterparts – its camouflage is far from perfect, it is permanently tethered to cumbersome wires, and its changing colours have to be controlled by an operator. But it’s certainly a cool (and squishy) step in the right direction.
The camo-bot is an upgraded version of a soft-bodied machine that strode out of George Whitesides’ laboratory at Harvard University last year. That white, translucent machine ambled about on four legs, swapping hard motors and hydraulics for inflatable pockets of air. Now, Morin has fitted the robot’s back with a sheet of silicone containing a network of tiny tubes, each less than half a millimetre wide. By pumping coloured liquids through these “microfluidic” channels, he can change the robot’s colour in about 30 seconds.
Jerka was the first. The 20-year-old polar bear was born in captivity, and had lived in Germany’s Wuppertal Zoo since the age of two. In the summer of 2010, she started suffering from epileptic seizures and eight days later, on the 16th of June, she finally passed away. Lars, a male bear who lived in the same enclosure, also became seriously ill. He was hooked up to an IV drip and treated with anti-seizure medicine. It took several weeks, but he eventually made a full recovery.
When the zookeepers dissected Jerka’s body, they found signs of inflammation in her brain. The pattern of damage pointed to a viral infection, but no one knew which virus was responsible. A team of scientists led by Alex Greenwood from the Leibniz-Institute for Zoo and Wildlife Research searched Jerka’s brain tissue for the genetic material of many possible viruses, from rabies to canine distemper virus. They found only one hit, and it looked a lot like EHV1 – a virus that infects horses.
A.ervi attacks a pea aphid, by Alexander Wild
In a British lab, a wasp has become (locally) extinct. And then, another wasp follows it into oblivion. That’s odd because these two insects are not competitors. They don’t attack one another, and they don’t even eat the same food. They do, however, remind us that it’s very hard to predict how the decline of one species will affect those around it.
Some consequences are obvious. If an animal goes extinct, its loss will cascade up and down the food web, so that its predators will suffer but its prey will probably thrive. But food webs are webs for a reason, rather than a set of isolated linear “food chains”. Consequences can ripple across, as well as up and down.
One does not simply start mummifying one’s dead. Mummification is a technically challenging business that involves sophisticated tricks for preparing a corpse. It’s also steeped in intricate cultural traditions. How does such a practice start?
Chilean scientist Pablo Marquet has tried to answer that question by studying the world’s oldest mummies – those created by the Chinchorro people of northern Chile. The Chinchorro were preserving their dead some two thousand years before the Egyptians started doing so. Rather than just mummifying their elites, the Chinchorro preserved all of their dead – man and woman, elderly and infants. They went to great pains to do so. They would remove the organs and muscles of their dead, reinforce the skeletons with sticks, and fill the bodies with earth and vegetation to get the right shape. They covered the body in a mud coat and clay mask, and decorated it with colour.
Marquet thinks he knows why these practices began. Rather than simply looking at cultural factors, he has intimately tied the practice into changing climates and shifting population sizes. At the time that they started mummifying cadavers, the Chinchorro had gone through a population boom, driven by rich coastal seas. But they also lived in the Atacama Desert: the so-called driest place on Earth. In such an arid environment, any buried corpses would have taken their time to decay, if they did at all. The very land around them naturally mummified the corpses, and the Chinchorro simply followed suit.
I was at the Ecological Society of America’s Annual Meeting when I saw this tweet:
For those of you who are wondering how you weaponise shark teeth, which are already regenerating, serrated meat knives at the business end of a streamlined, electric-sensing torpedo, here’s how. You drill a tiny hole in them, and then bind them in long rows to a piece of wood to make a sword. Or a trident. Or a four-metre-long lance. And then, presumably, you hit people really hard with them.
That’s what the people of the Gilbert Islands have been doing for centuries. Sharks are an ingrained part of their culture and their teeth have been an ingrained part of their weapons. Tiger sharks feature heavily – they have thick, cleaver-like teeth that can slice through turtle shells so they make a good cutting edge. But the weapons also include the teeth from spottail, dusky and bignose sharks (you can identify species from their teeth), and none of these actually live around the Gilbert Islands today.
Drew, who studied 124 of these weapons, says that their teeth reveal a “shadow diversity” – traces of sharks that disappeared from the surrounding waters before we even knew they were there. I wrote about this story for Nature News – head over there for the full details.