If wasps didn’t exist, picnics would be a lot more fun. But the next time you find yourself trying to dodge a flying, jam-seeking harpoon, think about this: without wasps, many of your ingredients might not exist at all. Irene Stefanini and Leonardo Dapporto from the University of Florence have found that the guts of wasps provide a safe winter refuge for yeast – specifically Saccharomyces cerevisiae, the fungus we use to make wine, beer and bread. And without those, picnics would be a lot less fun.
S.cerevisiase has been our companion for at least 9,000 years, not just as a tool of baking and brewing, but as a doyen of modern genetics. It has helped us to make tremendous scientific progress and drink ourselves into stupors, possibly at the same time. But despite its significance, we know very little about where the yeast came from, or how it lives in the wild.
The wild strains do grow on grapes and berries, but only found on ripe fruits rather than pristine ones. And they’re usually only found in warm summery conditions. So, where do they go in the intervening months, and how do they move around? They certainly can’t go airborne, so something must be carrying them.
Stefanini and Dapporto thought that wasps were good candidates. They’re active through the summer, when they often eat grapes. Fertilised females hibernate through the winter and start fresh colonies in the spring, feeding their new larvae with regurgitated food. In the digestive tracts of wasps, yeasts could get a ride from grape to grape, from one wasp generation to the next, and from autumn to spring.
There’s a microscopic fungus that can starve nations and punch through Kevlar. It kills on such as scale that its effects can be seen from space. It’s called Magnaporthe oryzae and it causes a disease known as rice blast. The fungus doesn’t infect humans, but it does kill rice. It kills a lot of rice, destroying up to 30 per cent of the world’s total crop every year – enough to feed 60 million people. Slowly, scientists have worked out how this cereal killer claims its victims.
A rice plant’s woes begin when one of the fungal spores lands on its leaves. As soon as it is surrounded by water, the spore sprouts a dome-shaped structure called the appressorium. This is infection HQ – it’s what the fungus uses to break into the plant. Once inside, it reproduces, eventually causing lesions that kill the leaf.
The appressorium produces glycerol as it grows, which lowers the relative amount of water inside the dome, and draws water in from outside. This builds up enormous pressure, around 40 times more than that within a car tyre. That pressure is directed into a narrow ‘penetration peg’ that travels through a pore at the bottom of the dome, and pierces the helpless plant.
One of the most successful alliances in the natural world often goes unnoticed. It involves either an alga or a bacterium that harvests energy from the sun to make its own nutrients. It shares this bounty with a fungus, which reciprocates by providing it with shelter. Together, the associates form a dual organism known as a lichen.
This alliance is so successful that lichens have colonised every continent, including Antarctica. They’re often ignored, but look closely, and you’ll find a hidden world of jellies, bushes, worms and pixie cups. Look even closer, and you’ll find a world of poison.
Ulla Kaasalainen from the University of Helsinki has discovered that one in eight species of lichens wield microcystins, a group of poisons that cause liver damage in humans and other animals. These chemicals are manufactured by blue-green bacteria known as cyanobacteria. These microbes are best known for creating large ‘blooms’ in lakes and rivers, which discolour the water with greenish swirls, and poison it with harmful toxins like microcystins. These toxins can accumulate in the food chain, affecting humans via shellfish and fish.
A leaf falls from the rainforest canopy, but it never hits the ground. Instead, it becomes trapped by nets of sticky fungi. While other lost leaves litter the forest floor, this one has joined the jungle’s mezzanine level – a layer of litter suspended in mid-air and hanging by a thread.
The fungi belong to a single genus called Marasmius, which extend networks of root-like filaments through the air. They act like a web that catches falling matter from the branches above. They have gone unappreciated, but Jake Snaddon from the University of Oxford has found just how important they can be.
By snaring leaves, the fungi provide room and board to insects, spiders and other canopy creepy-crawlies that might otherwise be confined to the ground. When Snaddon removed the fungi, the numbers of these animals plummeted by 70 percent.
Every time you drink a pint of lager, you owe a debt to a small fungus that lives in the beech forests of Patagonia. This previously undescribed species – Saccharomyces eubayanus – merged with a close relative to create a hybrid, whose fermenting abilities produce all of today’s lagers. Without it, our pints would have a much darker complexion.
Ask someone to think of a domesticated species and they’ll probably think of something like a dog, cat, cow or horse. But domesticated fungi are just as close to our hearts or, at least, our livers. The yeast, Saccharomyces cerevisiase, has been used to bake bread and ferment wine or ales for centuries. But it’s only partially involved in lagers.
Lager is fermented at a lower temperature than either ale or wine, and the fungus for the job is a cold-tolerant species called S.pastorianus. It has never been found in the wild, and its genes tell us why. It has four of each chromosome, and appears to be a fusion of two different yeast species. One of these is S.cerevisiae but the identity of the second partner has been a long-running mystery. Until now, the best guess was yet another species of cold-tolerant yeast called S.bayanus. But like S.pastorianus, S.bayanus has never been found in the wild.
The planet’s land plants are engaged in an ancient alliance with the so-called “AM fungi” that grow into their roots. One plant might be colonised by many fungi, and a single fungus could connect up to many plants. The fungi harvest nutrients like phosphorus and nitrogen from the soil and channel them to their hosts. In return, the plants provide the fungi with the sugars and carbohydrates they need to grow.
This symbiotic partnership covers the planet in green. It’s common to 80 percent of land plants, and is credited with driving the evolution of this group some 470 million years ago. Now, Toby Kiers from Vrije University in Amsterdam has found that plants and fungi have maintained their grand alliance by setting up a strong market economy.
Most life on this planet goes about their business as single cells. Only rarely do these singletons unite in cooperative societies, creating bigger and more complex living things, from trees to humans. This transition from single-celled to ‘multicellular’ life is one of the most important transitions in the evolution of life on Earth and it has happened many times over.
There are two main routes to a multicellular life. Single cells can merge together, and some modern species recap how this might have happened. Individual slime moulds join to form mobile slugs, while myxobacteria can merge into predatory swarms. Alternatively, cells can multiply but remain attached, staying united in their division. The choanoflagellates, possibly the closest living relatives of animals, can do this, creating simple colonies from single cells.
So we have a reasonable, if basic, understanding of how multicellular creatures first evolved. But we’re still largely in the dark about why. What benefit did cells gain from sticking together, rather than swimming solo? John Koschwanez from Harvard University thinks he has one answer: by sticking together, clumps of cells became better at foraging for nutrients. The multicellular life was a well-fed one.
Meet our newest potential weapon against malaria – a fungus loaded with a chemical found in scorpion venom. Metarhizium anisopliae is a parasitic fungus that infects a wide variety of insects, including the mosquitoes that spread malaria. Their spores germinate upon contact and the fungus invades the insect’s body, slowly killing it. Now, Weiguo Fang from the University of Maryland has modified the fungus to target the malaria parasites lurking inside the mosquitoes.
Fang loaded the fungus with two chemicals that attack the malaria parasite Plasmodium falciparum. The first is a protein called SM1 that prevents the parasites from attaching to the mosquito’s salivary glands. By blocking Plasmodium‘s path, SM1 stops the parasite from travelling down the mosquito’s mouthparts into the people it bites. The second chemical is scorpine – a toxic protein wielded by the emperor scorpion, which kills both bacteria and Plasmodium. This double whammy of biological weapons slashed the number of parasites in mosquito saliva by 98%.
Flatfish are the closest living relatives to swordfish and marlins
At first glance, a swordfish and a flounder couldn’t seem more different. One is a fast, streamlined hunter with a pointy nose, and the other is an oddly shaped bottom-dweller with one distorted eye on the opposite side of its face. Their bodies are worlds apart, but their genes tell a different story.
Alex Little from Queen’s University, Canada, has found that billfishes, like swordfish and marlin, are some of the closest living relatives to the flatfishes, like plaice, sole, flounder and halibut. This result was completely unexpected; Little was originally trying to clarify the relationship between billfishes and their supposed closest relatives – the tunas. That connection seems to make more sense. Both tunas and billfishes are among a handful of fish that are partially warm-blooded. They can heat specific body parts, such as eyes and swimming muscles, to continuously swim after their prey at extremely fast speeds with keen eyesight.
But it turns out that these similarities are superficial. Little sequenced DNA from three species of billfishes and three tunas, focusing on three parts of their main genome and nine parts of their mitochondrial one (a small accessory genome that all animal cells have). By comparing these sequences to those of other fish, Little found that the billfishes’ closest kin are the flatfish and jacks. Indeed, if you look past the most distinctive features like the long bills and bizarre eyes, the skeletons of these groups share features that tunas lack. Indeed, billfish and tuna proved to be only distant relatives. Their ability to heat themselves must have evolved independently and indeed, their bodies product and retain heat in quite different ways.
Little’s work is testament to the power of natural selection. Even closely related species, like marlins are flounders, can end up looking vastly different if they adapt to diverse lifestyles. And distantly related species like tuna and swordfish can end up looking incredibly similar because they’ve adapted to similar challenges – pursuing fast-swimming prey. This shouldn’t come as a surprise – a few months ago, a French team found that prehistoric predatory sea reptiles were probably also warm-blooded.
Reference: Molecular Phylogenetics and Evolution: http://dx.doi.org/10.1016/j.ympev.2010.04.022; images by Luc Viatour and NAOA
Ancient death-grip scars caused by fungus-controlled ants
Forty-eight million years ago, some ants marched up to a leaf and gripped it tight in their jaws. It would be the last thing they would ever do. Their bodies had already been corrupted by a fungus that, over the next few days, fatally erupted from their heads. The fungus produced a long stalk tipped with spores, which eventually blew away, presumably to infect more ants. In time, all that was left of this grisly scene were the scars left by the ants’ death-grip. Today, David Hughes from Harvard University has found such scars in a fossilised leaf from Germany.
Today, hundreds of species of Cordyceps fungi infect a wide variety of insects, including ants. Like many parasites, they can manipulate the way their hosts behave. One species, Cordyceps unilateralis, changes the brains of its ant hosts so that they find and bite into leaves, some 25cm above the forest floor. The temperature and humidity in this zone are just right for the fungus to develop its spore capsules. In its dying act, the ant leaves a distinctive bite mark that’s always on one of the leaf’s veins on its underside. And that’s exactly what Hughes saw in his fossil leaf.
Hughes originally thought that the marks were made by an insect cutting the veins of the leaf to drain away any potential poisons, something that modern insects also do. But these marks look very different – those on the fossil leaf bear a much closer resemblance to those of Cordyceps-infected ants. This is the first fossil trace of a parasite manipulating its host, but it’s not the oldest evidence for such a relationship. In 2008, another American group found a 105-million-year-old piece of amber containing a scale insect, with two Cordyceps stalks sticking out of its head. The war between insects and their Cordyceps nemeses is an ancient one indeed.
This article is reposted from the old WordPress incarnation of Not Exactly Rocket Science.
Cowboys have been lassoing cattle for several centuries, but it turns out that fungi developed the same trick 100 million years ago when dinosaurs still walked the Earth.
Alexander Schmidt and colleagues from the Humboldt University of Berlin found evidence of this ancient Wild West scene in a beautiful chunk of French amber.
The amber piece lacked the transparent clear beauty of a jeweller’s piece and the debris and dirt inside it suggests that it came from tree sap that had fossilised after it had fallen to the ground. There, it perfectly preserved the species living in the leaf litter, including a species of predatory fungi and the small worms – nematodes – that Schmidt thinks it hunted.
The fungus’s weapons were single cells coiled into rings just 10 micrometres in diameter. A thousand of these tiny loops could fit in a centimetre, but they were more than large enough to accommodate a blundering nematode. Once a worm swam through, the fungi constricted its snare, trapping the animal.
The cellular lassos sometimes broke off from the main fungal cells and Schmidt found that many of these loose rings clumped together. According to him, this probably means that the rings were coated with a sticky glue to better ensnare their nematode prey.