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  • [♪ INTRO]

  • Ever since humans found out germs were a thing,

  • we've had a vendetta against microbes.

  • The idea that death can be doled out by stuff we can't even see

  • is pretty unsettling.

  • So we invented antibacterial soap and antibiotics and antifungals,

  • and we went a little bit overboard in the end with the anti-everythings.

  • And as a result, we've often ignored the existence of good microbes.

  • With the exception of the ones that give us cheese and yogurt

  • and beer and bread, of course.

  • We've always given them a free pass.

  • But good microbes do a lot more than make yogurt yogurty

  • and cheese cheesy.

  • They also help us digest food and fight illness.

  • And the more we've learned about them, the more we've realized

  • that they have the capacity to do really big things.

  • Like help us protect endangered species and maybe even undo

  • some of the big mistakes we have made as humans.

  • So here are six examples of microbes helping to save the world.

  • The first, koalas. They are notoriously picky eaters.

  • Although they've occasionally been seen eating leaves

  • from other trees, for the most part, they eat eucalyptus leaves.

  • And that's pretty much it.

  • And they're even picky about which species of eucalyptus they eat.

  • So, these things are cute, but they're also, like,

  • the worst dinner guests of all time.

  • Thankfully, that's not too much of an issue for them.

  • Australia is full of eucalyptus trees, and there isn't a lot of competition

  • for it since the plant's leaves are toxic.

  • Koalas can only digest it thanks to a special type of gut bacteria

  • one they acquire as babies when they eat what's called pap.

  • That's a special kind of microbe-rich poop

  • that they get from their moms.

  • So overall, this lifestyle works for them. Or it did.

  • In the next sixty years, climate change is expected to

  • reduce the distribution of most Australian eucalyptus species

  • by more than half.

  • Urbanization and habitat destruction are also a threat,

  • and that was before the devastating Australian wildfires

  • (which started in 2019) added even more pressure.

  • In response to this, you would think koalas might switch

  • to another food source.

  • But they don't always do thatin part, because

  • their digestive systems are just so specialized

  • to one or a few species of eucalyptus.

  • Fortunately, there's a pap for that.

  • In 2019, scientists successfully transplanted the gut bacteria

  • from koalas who ate one type of eucalyptus, called messmate,

  • into the guts of those who were used to eating another type,

  • called manna gum.

  • Specifically, they gave the manna gum koalas capsules

  • that contained microbes extracted from the poop of messmate koalas.

  • Which is like, you know, slightly less gross than eating actual poop.

  • The scientists hoped that the unique microbes from the messmate koalas

  • would help the other group's bodies digest the new food.

  • And at the end of the experiment, the manna gum eaters

  • were eating more messmate. Sosuccess!

  • To be fair, though, the researchers weren't totally sure

  • if this happened because of the increase in gut bacteria,

  • or if the gut bacteria were increasing because the koalas were eating

  • more messmate for some other reason.

  • So there's room here for more research.

  • But it's intriguing to think that poop and the bacteria it contains

  • might one day help save a species.

  • To the delight of poop joke enthusiasts everywhere.

  • Next, malaria is one of humanity's most deadly foes.

  • But we aren't the only species that gets it.

  • Bats, reptiles, birdsthere are a lot of animals on malaria's hit list,

  • although not all of them are affected by it the way we are.

  • Take avian malaria, for example.

  • Although it can shorten birds' lives, it usually doesn't kill them.

  • In some isolated places, though, avian malaria can be deadly. Like in Hawai'i.

  • Until humans came along, birds in Hawai'i had no exposure

  • to the malaria parasitebecause there were no mosquitos

  • on the Hawaiian Islands.

  • According to a local legend, that only happened when a bunch of sailors

  • dumped a barrel full of water and mosquito larvae

  • into the wetlands around Lahaina.

  • Whichdid that seem like a good idea?

  • When the mosquitos arrived, so did the avian malaria parasite.

  • And after native Hawaiian birds were introduced to it,

  • ten species went extinct.

  • Thankfully, there might be a way to control this disease in Hawai'i

  • and all over the world.

  • And it's not insecticidebecause although that's been the standard for years,

  • mosquitos have an annoying habit of becoming resistant to it.

  • Instead, scientists are testing a new weapon: a bacteria called Wolbachia,

  • which naturally infects a lot of other insects,

  • but not malaria-carrying mosquitos.

  • But in a 2009 experiment, scientists took some Wolbachia

  • and managed to infect a group of Aedes aegypti mosquitoes with it.

  • Those are mosquitos that carry a whole bunch of diseases,

  • including avian malaria.

  • Then, they had those mosquitos drink the blood of chickens

  • infected with the avian malaria parasite.

  • And normally, this would result in the insects becoming malaria carriers.

  • But in this case, the mosquitos actually appeared to have

  • a stronger immune response, and fewer malaria parasites developed.

  • Right now, scientists aren't completely sure why this works,

  • but it could be because the mosquito's immune system

  • gets a boost in the presence of Wolbachia.

  • And as a bonus, this method also works to prevent other diseases,

  • including mosquito-borne human ones like dengue and Zika,

  • which are also carried by A. aegypti.

  • If you've ever tried to enjoy a day at one of the Midwest's Great Lakes,

  • you may have noticed a bunch of tiny, pokey shells all over the beach.

  • Those are invasive zebra mussels, and they're there just to ruin your afternoon.

  • Or so it seems like, anyway.

  • In reality, invasive mussels are a huge problem

  • not just because it hurts to step on them,

  • but because they are extremely difficult to control.

  • Juveniles are microscopic and will attach themselves to almost any hard surface,

  • which means boat owners can accidentally transport them from one lake to another.

  • And when they do, these mussels clog the intake pipes

  • that feed city water supplies, they hog nutrients, and they steal food

  • from native fish and other aquatic species.

  • In the US, they cost the economy around a billion dollars every year.

  • Fortunately, scientists have figured out how to use

  • the mussels' own diet against them.

  • See, mussels usually eat plankton,

  • but they also eat bacteria.

  • And after testing more than 700 strains, researchers learned that a common,

  • usually harmless bacteria called P. fluorescens produces a toxin

  • that's dangerous to the mussel's digestive system.

  • It causes cells to rupture and die in the mussels' digestive gland,

  • and that ultimately kills the animal.

  • Maybe more importantly, though, when mussels feed on this bacteria,

  • they don't notice anything's wrong; they seem to think they're having

  • just a nice and lovely day.

  • And they will keep eating until they die.

  • This is huge, because although chemicals like chlorine

  • are a more obvious threat to the animals, mussels can sense

  • those chemicals and will shut their valves to protect themselves.

  • The bacteria, meanwhile, just masquerades as normal food.

  • Scientists have been looking into this biological solution

  • to the invasive mussel crisis for decades, but in the last few years,

  • that research has finally started translating into practical use.

  • So someday, we might be thanking P. fluorescens for our clean,

  • mussel-free beaches.

  • A common forest salamander has a weird way of weaving

  • in and out of its clutch of eggs.

  • And it's not just being mysterious: It's transferring an antifungal bacteria

  • from its skin onto its eggs.

  • The bacteria helps protect the eggs from a common type of fungus.

  • But when scientists saw this, they wondered if there might be

  • another application for that antifungal.

  • They wanted to know if it could also be used to prevent a deadly

  • chytrid fungus, which infects more than 500 amphibian species

  • around the world.

  • Biologists have tried a number of strategies to control this fungus,

  • but none of them seem practical for large populations,

  • and others have had nasty side effects.

  • So hey, maybe this salamander stuff could be the solution.

  • In 2009, researchers tested their hypothesis on mountain yellow-legged frogs,

  • which are very susceptible to chytrid.

  • It attacks tadpoles' mouths and damages adults' skin,

  • so infected frogs typically die.

  • In their experiment, scientists bathed frogs in a bacterial soup

  • made from J. lividum, the same bacteria found on the skin

  • of those salamanders.

  • And when those frogs were exposed to the fungus, none of them died.

  • Meanwhile, frogs who didn't get a bacterial bath weren't so lucky.

  • Over 80 percent of them didn't survive the fungus.

  • This treatment seems to work because the bacteria produces an antifungal

  • called metabolite violacein, which inhibits the fungus somehow.

  • Scientists have tried to figure out how this works, but they're not sure.

  • They think it might be a byproduct of violacein's interactions

  • with other bacteria.

  • In any case, it works, so they're going to keep doing it

  • and not just for the amphibians.

  • Because violacein also has antibacterial and even anti-cancer properties.

  • So it might be able to protect us, too.

  • You might not see it when you look at them, but coral really need algae.

  • The coral provides the algae with a safe place to live,

  • and the algae give the coral all kinds of nutrients it needs to survive.

  • So when that relationship is disrupted, bad things happen.

  • Like coral bleaching.

  • In the presence of stressors like rising temperature,

  • corals expel their algae, which makes the coral turn white

  • and become vulnerable to disease.

  • Bleaching can also stunt their growth

  • and negatively affect their ability to reproduce.

  • And a severe bleaching event can kill them.

  • When we filmed this in early 2020, 27% of the world's coral reefs

  • had already been lost due to bleaching,

  • and experts think that number is likely to go up.

  • But maybe it doesn't have to.

  • In 2018, researchers created a cocktail of different microorganisms,

  • each of which possessed certain protective qualities.

  • Some were chosen for their ability to produce catalase,

  • which can reduce the concentration of dangerous,

  • reactive oxygen speciesones that would damage proteins

  • or genetic material and kill cells.

  • Other microbes were good at converting nitrogen

  • into a nutrient the corals could use, while others

  • were aggressive toward pathogens.

  • And when scientists added these microbes to a coral community,

  • they reduced bleaching in the presence of warmer water and pathogens!

  • Which is great!

  • That doesn't mean the microbes prevented or reversed bleaching, though

  • they were just able to help the coral survive the bleaching event

  • with fewer ill effects.

  • It still takes a reduction in water temperature and the return of algae

  • to get the coral back on track.

  • But maybe something like this could keep corals afloat

  • during short warm spells.

  • Finally, cleaning the messes humans have made remains

  • one of our biggest challenges.

  • And nowhere is this more evident than in superfund sites.

  • These are some of the most polluted places in the United States,

  • and they get their name, superfund, from the trust Congress established

  • to help pay for their cleanup.

  • Not superfun (it's hard to say it), superfund.

  • And that cleanup is expensive and it's dangerous

  • for humans and for our non-human helpers.

  • Poplar trees, for example, can naturally help remove

  • a common industrial solvent called trichloroethylene, or TCE,

  • from heavily-contaminated sites.

  • But in the process, the toxicity may cause them to become stunted:

  • Their leaves can turn yellow, and their branches can wither.

  • Some may even die.

  • So, there's a balance here.

  • Because trees are a great way to clean up polluted areas

  • but we also don't want to kill them.

  • Cue the microbes!

  • In 2017, researchers discovered that poplar trees fortified

  • with a kind of Enterobacter bacteria were able to remove the TCE

  • with fewer ill effects.

  • This specific strain of Enterobactercalled PDN3 — breaks down the TCE

  • and releases a harmless chloride ion instead.

  • Researchers inoculated poplar trees by exposing their roots to the bacteria

  • for one week, then checking to make sure that the bacteria was able to

  • colonize the roots.

  • The trees that were inoculated not only removed more TCE from the environment,

  • but they were also healthier and larger than the trees

  • that didn't get any microbial assistance.

  • Because, like, when a toxin isn't trying to wither your leaves and kill you,

  • it turns out you can do your job better.

  • So, despite our aversion to them, because yes, they can kill you,

  • almost all microbes are either benign or positive.

  • They make your yogurt yogurty and they make your cheese cheesy.

  • But more than that, they can also help

  • or even save species across the planet.

  • If you want to learn more about microbes, good news: