6 Bacteria with Awesome Superpowers


[ ♪ Intro ♪ ] Bacteria. They’re never going to officially become
superheroes in the Marvel or DC universes, but some of them probably should be. They’ve been around for about 3.5 billion
years, and some of them have also evolved pretty incredible abilities, which let them
survive in almost every potential scenario on Earth. They might not have cool costumes like Captain
America or Wonder Woman, but here are six bacteria with amazing superpowers. First, there’s Geobacter metallireducens. Like all living things, this bacteria needs
to generate energy. But instead of using oxygen or carbon dioxide,
like many animals and plants, it does so using electrical current. Which should not even be possible. They produce energy using cellular respiration
— a process which also makes excess electrons that have to be dumped somewhere. A common electron acceptor, or oxidizing agent,
that cells use to complete this chemical reaction is oxygen. That’s what humans use, which is why you
and I need to breathe. But G. metallireducens lives underwater, in
sediments where oxygen is in short supply… so it uses iron and manganese from the environment
instead. It grows tiny hairlike structures called pili
to transfer electrons to the metal — these are essentially biological wires through which
electric current is flowing. If it runs out of metal, it can even grow
a little tail called a flagellum to swim to a new location, following chemical signals
to find the materials it needs. And, like any good superhero, this bacteria
is also sneaky when it comes to using its powers. Researchers didn’t find out it uses electricity
by seeing it in action — because to save energy, G. metallireducens only grows pili
or a flagellum when it needs them. Instead, scientists figured this out when
they sequenced the bacteria’s genome and found the genes that code for flagella! Apparently even superheroes can’t hide from
DNA sequencing. The next super bacteria is Deinococcus radiodurans. Its power has landed it in the Guinness Book
of World Records, where it’s listed as the world’s most radiation-resistant life form. It can survive being blasted with 1.5 million
rads of gamma radiation — which is at least a thousand times the amount it would take
to kill a human. It was discovered in 1956, when scientists
were experimenting with using radiation to sterilize canned food. Which isn’t as scary as it sounds — it’s
actually totally safe and is still done sometimes today. But the researchers working on this were amazed
when one can of meat spoiled anyway. The ruined can contained a mysterious red
substance… which turned out to be a colony of D. radiodurans. This bacteria has a couple of different ways
of protecting itself from intense radiation. For one thing, it produces high levels of
protective antioxidants — including carotenoids, the same compounds that make carrots orange,
and give the bacteria that characteristic reddish color. Antioxidants counter the destructive effects
of free radicals, highly reactive molecule fragments produced by radiation. That’s because they can offer up electrons
to stabilize free radicals without becoming destabilized themselves. Every D. radiodurans cell also contains four
to ten copies of its genome, so that it can recreate DNA sequences destroyed by radiation. It stitches together backup bits using a special
protein called RecA. Now, high doses of gamma rays aren’t exactly
a problem you often run into on Earth. So D. radiodurans probably evolved these abilities
to survive extreme dehydration, which can have similar destructive effects. Today, scientists think they may be able to
put it to use cleaning up toxic waste sites with radiation levels that would destroy most
microbes. They’ve also managed to splice in genes
from another bacteria species to create a strain of D. radiodurans that can break down
an organic compound called toluene, which is a common contaminant in toxic waste sites. So someday, a microbe that’s spoiled our
food could also be saving us from toxic waste! Most movie and comic book superheroes probably
enjoy munching on something like, say, shawarma, after saving the universe. But Ideonella sakaiensis prefers something
a little crunchier — like plastic. Specifically, polyethylene terephthalate,
or PET. Whether you know it or not, you probably use
this stuff every day. It’s a lightweight, colorless, strong plastic
that’s used in everything from disposable water bottles to polyester clothes. But this material is really hard to break
down… unless you’re I. sakaiensis. A team of Japanese scientists discovered this
plastic-eating bacteria in 2016, while hoping to find something that could break down PET,
and they eventually published their results in the journal Science. They started by collecting 250 sediment, soil,
and water samples from a plastic bottle recycling site. Then, back in the lab, they checked each sample
to see if any microbes in it were consuming PET and using it to grow — and one of them
was. The bacteria they found use at least two enzymes
to digest PET. First, they stick to the plastic’s surface
and secrete an enzyme into it, dubbed PETase, that breaks it down into an intermediate chemical
called MHET, which is absorbed into the cell. Then, other enzymes break MHET down even further,
producing carbon and energy that the bacteria can use. Depending on the temperature, it would take
a community of these bacteria about six weeks to totally break down a thin film of PET. And scientists hope that someday, these plastic-munching
microbes may play a role in keeping waste out of landfills. The world’s strongest glue isn’t on the
shelves of your local hardware store — or in Spider-Man’s webs. It’s made by a bacteria called Caulobacter
crescentus, and this adhesive was described in 2006 in the Proceedings of the National
Academy of Sciences. This microbe usually colonizes wet surfaces
like boat hulls, and once it does, it’s really tough to clean it off, even with something
like a pressure washer. It adheres to these surfaces using a natural
glue-like substance made out of molecules called polysaccharides, or long chains of
sugars linked together. Sticking to a surface provides the bacteria
with a stable environment, where potential food might settle. A team of scientists had been studying other
aspects of C. crescentus’s biology, but they decided to test its adhesive powers after
noticing how hard it was to remove it from glass plates. They grew individual bacteria cells on the
tips of flexible pipettes, and then used a second pipette to try and pull the cells off. Based on how far the flexible pipette bent
before the cell came loose, they could calculate the force involved. It turns out it takes around 70 newtons per
square millimeter to rip a C. crescentus cell from a surface. This means the bacteria are about seven times
stronger than geckos’ famously sticky footpads and almost three times as strong than commercial
superglue. They’re sticky enough that you could suspend
several cars from a quarter-sized spot of this glue. Take that, Peter Parker. To avoid wasting any glue or sticking itself
to the wrong thing, this bacteria needs to apply its glue precisely and efficiently. Each cell has a flagellum, and when that flagellum
comes in contact with a surface, nearby pili jump in to stabilize it and keep it from moving. This stimulates the cell to start producing
glue. Because it works even in wet conditions, scientists
think the sticky, sugary substance might have applications as a surgical adhesive. So C. crescentus could be coming soon to an
operating room near you. Many bacteria are known for being able to
tolerate extreme heat. But some of the most heat-tolerant of them
all come from the genus Aquifex. Which kind of already sounds like a superhero’s
name. These thermophiles — which literally means
“heat-lovers” — live in places like the hot springs in Yellowstone National Park,
where the water can get up to 100 degrees Celsius. There, they grow in all sorts of cool-looking
white and pink mats and streamers. Like other thermophiles, they thrive in such
hot environments thanks to adaptations like special proteins, which don’t unravel at
high temperatures. But living in hot water isn’t Aquifex’s
only superpower. These bacteria are also called chemolithoautotrophic,
which means they get their energy from inorganic compounds in their environment. They fuel their cells with molecules like
hydrogen, carbon dioxide, mineral salts, and oxygen. And the fact that they use oxygen is pretty
surprising. Even though many bacteria like hot temperatures,
most of them are anaerobic, which means they don’t use oxygen to generate energy. In fact, most heat-loving bacteria will die
when they’re exposed to it. But for some reason, Aquifex has no problem
with oxygen — in fact, some kinds need it to stay alive. And it doesn’t even take much oxygen to
keep them going. They can survive with only a little bit of
it — somewhere around 8 parts per million. Because it can survive both extreme temperatures
and low levels of oxygen, Aquifex may even be useful in industry and other scientific
research. So even among thermophiles, this bacteria
is extra super. And finally, we have Neisseria gonorrhoeae. Which is exactly what you think it is. Normally, gonorrhea is only famous for being
a sexually-transmitted disease, but I’m guessing you don’t know about the other
wild thing these bacteria can do. According to a 2008 study from the journal
PLOS Biology, they are, gram-for-gram, the strongest organisms on Earth. Which might seem alarming. Gonorrhea use pili — those cable-like appendages
found on other bacteria — to crawl across surfaces and attach to and infect other cells. Scientists studying how these infections take
hold placed individual gonorrhea microbes in an array of stretchy gel pillars. When a bacterium grabbed at one of these tiny
pillars with its pili, the pillar would bend over, and the scientists could measure how
far they bent to calculate the amount of force being exerted. They aren’t sure why, but about 1 in 100
times, what started as a standard grab would keep going and get stronger… and stronger. Using an electron microscope, the scientists
confirmed that the bacteria were bundling additional pili together to exert more and
more force. These marathon tugging sessions could last
for hours and end up pulling ten times harder than when they started. A single gonorrhea bacterium could exert up
to about one billionth of a newton of force. That may not sound like a lot — but consider
how tiny one bacteria cell is. An individual gonorrhea microbe can pull 100,000
times its body weight, making this possibly the strongest biological force measured to
date. So basically, gonorrhea might just be Superman’s
Kryptonite. Which is a sentence I have never said before. The reason this bundling behavior hadn’t
been observed before is that a protein used to help study bacteria actually stops gonorrhea
from bundling their pili. Of course, we still don’t know much about
why this bacteria, of all things, evolved to be a tug-of-war champion — there’s still
a lot more to learn. But it’s definitely awesome. Remember, just because something is tiny,
that doesn’t mean it’s not powerful. And hopefully the stories of these sticky,
shocking, superhero microbes have increased your respect for the world of bacteria. Because comic superheroes have nothing on
these organisms. Thanks for watching this episode of SciShow! If you’d like to learn about another bacteria
with superpowers, you can watch our episode on a strange blue glow that saved lives during
the Civil War. [ ♪ Outro ♪ ]

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