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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.
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