Thanks to Brilliant for supporting this episode
of SciShow. Go to Brilliant.org/SciShow to learn how you
can take your STEM skills to the next level! [♪ 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 that — in 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. So… success! 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, birds — there 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 parasite — because 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. Which… did 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 insecticide — because 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 species — ones 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 Enterobacter — called
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: There is so much to learn about them, from
their behavior to their genetics. But if you really want to dive in, it might
be good to know a bit about computational biology. This field combines elements of physics, computer
science, and bio. And if you want to get a sense of what it
looks like, you can check out Brilliant’s Computational Biology course. It covers things like genomes, DNA composition,
and molecular folding — all things that are important in the lives
of microbes. And like all of Brilliant’s courses, it
does that in a really engaging, easy-to-understand way. So, props to them! If you want to check it out, you can go to
Brilliant.org/SciShow. And the first 200 people to sign up there
will get 20% off the annual Premium subscription. [♪ OUTRO]
