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Current time:0:00Total duration:11:19

Video transcript

hello and welcome to the wonderful world of fungi or fungi both are acceptable pronunciations but I say fungi because it's fungus not fungus though fungus is also fun to say fungi are a little bit like plants and more like animals than you might think 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 a hundred thousand or so of them those that we have met our wonderful weird and in some cases deadly the fact is death is pretty much what fungi are all about sure there are the fun fungi like the single-celled Saccharomyces also known as yeast without them we wouldn't have beer or wine or bread it's also true that fungi are responsible for all kinds of diseases from athlete's foot to potentially deadly histoplasmosis aka spelunkers lung caused by fungus found in bird and bat droppings fungi can even make people crazy when the fungus Clavis epps purpurea grows on grains used to make bread or beer it causes gangrene nervous spasms burning sensations loosen ations and temporary insanity one compound in this fungus lysergic acid is the raw material used to make LSD and finally there's the destruction that some fungi bring onto other animals 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 a third of all amphibians on earth but none of this is what I mean when I talk about fungi and death while some members of the fungus family are totalled bummers all of them together perform perhaps the most vital function in the global food web they feast on the deceased remains of almost all organisms on the planet and by doing that they convert the organic matter that we're all made of back into soil from which new life will spring so fungi they thrive on death and in the process make all life possible ah it 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 Louie pester in the form of a bio log R if e by pesters time beer had been brewed for thousands of years in cultures all over the world 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 but for all those money and no one understood how its most important ingredient worked until Brewers could actually see what yeast were doing the magic of fermentation was essentially magic Custer himself was never a big beer drinker but part of his academic duties and France required him to help find solutions to problems for the local alcohol industry and as part of this work in 1857 he began studying yeast under a microscope and discovered that they were in fact living organisms in a series of experiments on the newfound creatures he found that in the absence of free oxygen yeast were able to obtain energy by decomposing substances that contained oxygen we now know that pester 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 along the way Pistor also discovered that beer was often contaminated by other bacteria and fungi the growth of these beer spoiling microbes he found could be forded for up to 90 days by keeping the beer between 55 and 60 degrees celsius for a short period of time today we call that heating process pasteurization and it's used in everything from milk to canned foods to syrups to wines purposes the thing to hold on to here is Pasteur discovered that yeasts decompose sugars to get energy and it turns out most fungi spend most of their time decomposing all kinds of organic matter often the matter is dead when fungi get to it but not always when a tree or a person or a deer keels over fungi move in and start the work of decomposition same goes for that orange you forgot at the bottom of the fruit ball 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 thankfully the decomposition performed by fungi recycles the nutrients for the enjoyment of plants and animals as well as for other fungi all of this points to one of the main traits that all fungi have in common from single-celled yeast to giant multicellular mushrooms fungi like us are heterotrophs but instead of eating they absorb nutrition from their surroundings they do this mostly by secreting powerful enzymes that break down complex molecules into smaller organic compounds which they use to feed grow and reproduce most multicellular fungi contain networks of tiny tubular filaments called hyphy then grow through and within whatever they're feasting on 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 the inner woven mass of high fee that grows into the food source is called the mycelium and 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 my Celia are so densely packed that one cubic centimeter of rich soil can contain enough hyphy to stretch out one kilometer if you laid them into end so as high if you secrete the digestive enzymes fungi used the food to synthesize more proteins and the hyphy continued to grow allowing the fungi to conquer new territory and grow even more as a result fungi can get crazy big record-holding big a single honey mushroom and the Blue Mountains of Oregon is thought to occupy some 2386 acres by area the largest organism on the planet now there all kinds of crazy ways the fungi are classified but probably the easiest and most useful is organizing them by how they interact with other organisms the straight-up decomposers that break down dead stuff the mutual lists which form beneficial relationships with other organisms especially plants and then there are the Predators and the parasites decomposer fungi secrete enzymes that break down and absorb nutrients from nonliving organic materials such as that tree that nobody heard fall in the forest 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 the cycle of life they're pretty much the only organism that can do that they can even decompose proteins into component amino acids basically all the black it's in the soil in your backyard our tiny fragments of former plants digested by fungi mutualist fungi are a smaller group many have specialized - called historia that tangle themselves with plant roots for the benefit of both organisms these guys help plants absorb nutrients especially phosphates by breaking them down more efficiently than the roots can themselves in turn the fungi send out their - to the plants root tissue and withdraws like a finder's fee basically in the form of energy rich sugars sees me dualistic relationships are known as mycorrhizae from the Greek words mics or fungus and rise on or root mycorrhizae are enormous ly important in natural ecosystems as well as an agriculture almost all vascular plants in fact have fungi attached to their roots and rely on them for essential nutrients rows of barley the main ingredient in beer will even inoculate barley seed beds with specific mycorrhizal fungi to help promote growth other fungi aren't nearly so kind to their hosts predatory fungi actively capture prey with their hyphy soil fungus arthro betras uses modified hoops on its filaments to snare nematodes and absorb their inner tissue and there are the parasites those fungi that feed on living organisms without killing them at least for a while they one of my personal favorites the zombie ant fungus or oofy cordyceps it shoots spores into an ant where their high feet grow into its body and absorb nutrients from non-essential ant organs when the fungus is ready to reproduce it invades the ants brain and directs it to march to a cool moist location in the forest where its so-called fruiting spores erupt through the ants head to spread even more spores hmm and just to prove that even fungi have superheroes in 2012 scientists discovered that these zombie spores have themselves been targeted by another parasitic fungus not a lot is known about this ant saving fungus other than it sterilizes many of the zombie spores through a process like in to chemical castration that is so messed up weird all right now since I brought that up we should talk briefly about fungus sex fungi reproduce any way they can either sexually or a sexually some species even do it both ways but whichever way they choose most propagate themselves by producing enormous numbers of spores much like we saw in nonvascular plants and the simplest vascular plants the ferns but and this is a big but sexual reproduction in fungi isn't like sex in any other organism we've studied so far the concepts of male and female don't apply here at all some fungi reproduce on their own others can reproduce with any other individual that happens to be around and still others get only mate with a member of a different so-called mating type they're not different sexes they just have different molecular mechanisms that either make them compatible or not sometimes these types are called plus and minus and other times one and two in any case it's still considered sexual reproduction because each parent contributes genetic information when they make with the spore making it all starts with this beautiful chemical mating dances the mycelium from one fungus sends out pheromones that are picked up and bound to receptors by another willing and able partner this binding compels each mycelium to send its high feed toward the other when they meet they fuse the cytoplasm of their cells a stage of reproduction called plasma gimme some time 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 certain types of fungi including the tasty Morel produce spores and sack like a sigh contained in fruiting bodies known as ASCO carps that is the part that you pick when you're wandering through the forest some fungi shoot their spores off into the breeze other spores float away on the water 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 high feed do the tango finally for some fungi sexual reproduction just isn't all it's cracked up to be they'd rather just get on with it themselves some of these grow filamentous structures that produce spores by mitosis these structures are visible and they're called molds the stuff on the orange and the bottom of the fruit bowl or on the heel with a 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 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 since some species of yeast like our beer making friends Saccharomyces cerevisiae I convert sugars into alcohol brewers create conditions that encourage high rates of yeast production by giving them lots of sugar and oxygen since more yeast means alcohol so yeah fungi they feast on death and they can make us go and Satan turn ants into unholy zombies of the night but because of their hard work in strange ways they make possible stuff like agriculture and beer and everything else worth living for
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