Fungi: Death Becomes Them발음듣기
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Fungi: Death Becomes Them
101문장
100% 한국어
번역 8명 참여
출처 : 칸아카데미
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Male: Hello and welcome to the wonderful world of fungi or [funji]; both are acceptable pronunciations, but I say fungi because it's fungus, not [funjus], though [funjus] is also fun to say.발음듣기
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They diverged from protists about a billion years ago and today scientists estimate that there are about 1.5 million species of fungi on the earth, though in a formal taxonomic way, we only know about 100,000 or so of them, and those that we have met are wonderful, weird and in some cases, deadly.발음듣기
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It's also true that fungi are responsible for all kinds of diseases from athlete's foot to potentially deadly histoplasmosis, AKA Spelunker's Lung caused by fungus found in bird and bat droppings.발음듣기
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When the fungus Claviceps purpurea grows on grains used to make bread or beer, it causes gangrene, nervous spasms, burning sensations, hallucinations and temporary insanity.발음듣기
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More than 6 million bats in North America have died since just 2007 due to a fungal disease called White Nose Syndrome, and a fungus has been implicated in several extinctions of amphibians and threatens many more, perhaps as many as 1/3 of all amphibians on earth.발음듣기
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While some members of the fungus family are total bummers, all of them together perform perhaps the most vital function in the global food web.발음듣기
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By doing that, they convert the organic matter that we're all made of back into soil from which new life will spring.발음듣기
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(bopppy music) Aha! You didn't expect to see me in the chair so soon, but before we go any deeper into the kingdom fungi, I wanted to make a toast to Louis Pasteur in the form of a Biolo-graphy.발음듣기
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(1920's music) By Pasteur's time, beer had been brewed for thousands of years in cultures all over the world.발음듣기
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Some experts think it may have been the very reason that our hunter-gatherer ancestors started farming and cobbled together civilization in the first place.발음듣기
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Until brewers could actually see what yeast were doing, the magic of fermentation was essentially "magic."발음듣기
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Pasteur himself was never a big beer drinker, but part of his academic duties in France required him to help find solutions to problems for the local alcohol industry.발음듣기
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As part of this work in 1857, he began studying yeast under a microscope and discovered that they were, in fact, living organisms.발음듣기
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In a series of experiments on the new-found creatures, he found that in the absence of free oxygen yeast were able to obtain energy by decomposing substances that contained oxygen.발음듣기
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We now know that Pasteur was observing yeast undergoing the process of anaerobic respiration, AKA fermentation; breaking down the sugars in grains like malted barley and converting them into alcohol, carbon dioxide, and the range of flavors that we associate with beer.발음듣기
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Along the way, Pasteur also discovered that beer was often contaminated by other bacteria and fungi.발음듣기
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The growth of these beer-spoiling microbes, he found, could be thwarted for up to 90 days by keeping the beer between 55 and 60 degrees Celcius for a short period of time.발음듣기
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Today, we call that heating process pasteurization and it's used in everything from milk to canned foods to syrups to wines.발음듣기
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For our purposes, the thing to hold onto here is Pasteur discovered that yeast decomposed sugars to get energy.발음듣기
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When a tree or a person or a deer keels over, fungi move in and start the work of decomposition.발음듣기
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If it weren't for this fungal function, plants and the animals that eat them couldn't exist because the elements that they take from the soil would never return.발음듣기
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Thankfully, the decomposition performed by fungi recycles the nutrients for the enjoyment of plants and animals, as well as for other fungi.발음듣기
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From single-celled yeast to giant multi-cellular mushrooms, fungi, like us, are heterotrophs, but instead of eating, they absorb nutrition from their surroundings.발음듣기
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They do this mostly be secreting powerful enzymes that break down complex molecules into smaller organic compounds, which they use to feed, grow and reproduce.발음듣기
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Most multi-cellular fungi contain networks of tiny tubular filaments called hyphae, then grow through and within whatever they're feasting on.발음듣기
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Unlike plant cell walls, which are made of cellulose, the cell walls of fungi are strengthened by the nitrogenous carbohydrate, chitin, the same material found in the exoskeletons of insects, spiders and other arthropods.발음듣기
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It's structured to maximize its surface area, which as we've learned in both plants and animals, is the name of the game when it comes to absorbing stuff.발음듣기
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Mycelia are so densely packed that one cubic centimeter of rich soil can contain enough hyphae to stretch out one kilometer if you laid them end-to-end.발음듣기
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As hyphae secrete the digestive enzymes, fungi use the food to synthesize more proteins and the hyphae continued to grow, allowing the fungi to conquer new territory and grow even more.발음듣기
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A single honey mushroom in the Blue Mountains of Oregon is thought to occupy some 2,386 acres.발음듣기
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There all kinds of crazy ways that fungi are classified, but probably the easiest and most useful is organizing them by how they interact with other organisms.발음듣기
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The straight up decomposers that break down dead stuff, the mutualists which form beneficial relationships with other organisms, especially plants, and then there are the preditors and the parasites.발음듣기
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Decomposer fungi secrete enzymes that break down and absorb nutrients from non-living organic material such as that tree that nobody heard fall in the forest.발음듣기
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In fact, the ability of fungi to break down lignin, which is like what makes wood woody, and break it into glucose and other simple sugars, is crucial for this cycle of life.발음듣기
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Basically all the black bits in the soil in your backyard are tiny fragments of former plants digested by fungi.발음듣기
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Many have specialized hyphae called haustoria that tangle themselves with plant roots for the benefit of both organisms.발음듣기
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These guys help plants absorb nutrients, especially phosphates, by breaking them down more efficiently than the roots can themselves.발음듣기
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In turn, the fungi send out their hyphae into the plant's root tissue and withdraws like a finder's fee, basically, in the form of energy-rich sugars.발음듣기
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These mutualistic relationships are known as mycorrhizae, from the Greek words mykos, or fungus, and rhiza, or root.발음듣기
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Almost all vascular plants, in fact, have fungi attached to their roots and rely on them for essential nutrients.발음듣기
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Growers of barley, the main ingredient in beer, will even inoculate barley seed beds with specific mycorrhizal fungi to help promote growth.발음듣기
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The soil fungus arthrobotrys uses modified hoops on its filaments to snare nematodes and absorb their inner tissue.발음듣기
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Then there are the parasites, those fungi that feed on living organisms without killing them, at least for a while.발음듣기
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It shoots spores into an ant where their hyphae grow into its body and absorb nutrients from nonessential ant organs.발음듣기
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When the fungus is ready to reproduce, it invades the ant's brain and directs it to march to a cool, moist location in the forest where it's so-called fruiting spores erupt through the ant's head to spread even more spores.발음듣기
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Just to prove that even fungi have superheroes, in 2012 scientists discovered that these zombie spores have themselves been targeted by another parasitic fungus.발음듣기
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Not a lot is known about this ant-saving fungus, other than it sterilizes many of the zombie spores through a process likened to chemical castration.발음듣기
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Whichever way they choose, most propagate themselves by producing enormous numbers of spores, much like we saw in non-vascular plants and the simplest vascular plants, the ferns.발음듣기
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But, and this a big but, sexual reproduction in fungi isn't like sex in any other organism we've studied so far.발음듣기
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Some fungi reproduce on their own, others can reproduce with any other individual that happens to be around, and still others can only mate with a member of a different so-called "mating type."발음듣기
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They're not different sexes, they just have different molecular mechanisms that either make them compatible or not.발음듣기
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In any case, it's still considered sexual reproduction because each parent contributes genetic information when they make with the spore-making.발음듣기
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The mycelium from one fungus sends out pheromones that are picked up and bound to receptors by another willing and able partner.발음듣기
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When they meet, they fuse the cytoplasm of their cells; the stage of reproduction called plasmogamy.발음듣기
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Sometime between hours and centuries later, yes, it can literally take hundreds of years for fungi to have sex, this union leads to the production of spores that each fungus is then able to disperse.발음듣기
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Certain types of fungi, including the tasty morel, produce spores in a sac-like asci contained in fruiting bodies known as ascocarps.발음듣기
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More enterprising spores will hitch a ride on passing critters, hopefully, to be dropped off somewhere where there's plenty of nutrients to absorb so they, too, can grow, send out sexual pheromones when their time comes, and let their hyphae do the tango.발음듣기
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This stuff on the orange in the bottom of the fruit bowl or on the heel of the piece of bread that you left for a roommate who decided to leave it for the other roommate who thought that you'd rather have it.발음듣기
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In the unicellular yeast, the asexual reproduction occurs by old fashioned cell division or the formation of buds that get pinched off into separate organisms.발음듣기
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Since some species of yeast, like our beer-making friend Saccharomyces cerevisiae, convert sugars into alcohol, brewers create conditions that encourage high rates of yeast production, like giving them lots of sugar and oxygen since more yeast means more alcohol. So, yeah, fungi.발음듣기
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