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  • {♫Intro♫}

  • You might have been one of those lucky kids that, on your eighth birthday, got a microscope

  • to tinker with.

  • Maybe it came with some pre-made slides of hairs or onion root tips to introduce you

  • to the world of the tiny.

  • But they were just the beginning.

  • And if you missed out as a kid, it's not too late.

  • If you're interested in making your very own foray into the world of microscopy, here

  • are some of the creatures you might be able to spot with a home microscope -- and what

  • they can teach us.

  • First off, let's look at how microscopes let us see all these weird and wonderful little

  • things.

  • You're probably picturing a basic upright microscope, aka a compound microscope, and

  • that's exactly the kind we're thinking of.

  • Right at the base of the microscope is a light that shines up through a condenser lens, which

  • concentrates the light onto whatever you're looking at.

  • The image then shines up through an objective, which magnifies the picture.

  • The general setup looks kind of like one of those old-school overheadl projectors.

  • Then the lens in the eyepiece -- the part you have your eye squished against -- magnifies

  • the image one last time.

  • Depending on your microscope, these parts can do other things -- but this is the general

  • idea.

  • So the total amount a microscope can blow an image up is the magnifying power of the

  • objective lens multiplied by the power of the eyepiece.

  • The kind of microscope you'd be able to keep at home is generally able to magnify

  • things up to around one thousand times.

  • Microscopes more powerful than that exist, but unless you got a lot of scratch to throw

  • down, not super available for a hobbyist.

  • One of the creatures you might spot looks like a mix between a shovel, a vacuum cleaner,

  • and a jellyfish.

  • They're not animals, plants, or fungi.

  • Instead, they're a kind of single-celled protist.

  • Which is actually just a term microbiologists use to refer to any organism whose cells have

  • a nucleus, butisn't an animal, plant, or fungus.

  • More specifically, Giardia lamblia is a protozoan -- another catch-all term that refers to protists

  • that look more like animals than fungi or plants.

  • It's also a parasite known for causing the nasty diarrheal disorder giardiasis.

  • Giardia are found all over the world, so you could certainly find them in your backyard.

  • But you might want to be careful.

  • That's because they have a sneaky way of getting past our body's immune defenses

  • to cause infection.

  • They have what are called variant-specific surface proteins, or VSPs, on the surface

  • of their bodies.

  • This dense coat of proteins acts as a kind of shield against the acid in our stomachs

  • and the enzymes in our intestines.

  • Giardia also constantly change these proteins to match the digestive enzymes of a particular

  • host animal or to evade their host's immune system.

  • It's sort of like a protein disguise, lie they're wearing camo suits that are also

  • bulletproof.

  • They have these protein disguises because the host's immune system normally creates

  • antibodies that can bind to the surface of invading parasites and signal the body to

  • attack.

  • But it has trouble keeping up with Giardia's constantly shifting coat.

  • And in 2019, scientists found a way to use this trick to our advantage -- at least in

  • mice.

  • See, some scientists are working toward developing oral vaccines -- ones we can swallow instead

  • of getting a shot.

  • Not only would that be better for all the needle-phobes out there, but oral vaccines

  • could also be easier to distribute in the event of a pandemic.

  • You don't have somebody give you a shot in the arm you just get them

  • someone hands them to you and moves on.

  • But this is way easier said than done, because the harsh conditions of our stomachs are designed

  • to wear down things, and the parts of the vaccine that trigger an immune response get

  • pretty much digested before they can get to work.

  • So this study used VSPs as a protective shield for an oral influenza vaccine.

  • First, the researchers showed that Giardia VSPs can hold up in conditions similar to

  • the human gut by bombarding them with digestive enzymes and acids.

  • Then, they gave mice an oral influenza vaccine protected by VSPs.

  • Four weeks later, they exposed those mice to the flu.

  • The mice that had been given a vaccine protected by VSPs showed no signs of infection.

  • Mice who received an unprotected version didn't fare quite so well.

  • Even better, the VSPs seemed to work as an adjuvant -- a substance that's sometimes

  • added to vaccines to make the immune response more effective.

  • The next stop is to determine whether this approach works in humans.

  • If so, it's a pretty promising first step toward oral vaccines.

  • Not bad for a gut parasite.

  • Like Giardia, amoebas are protists.

  • They're a pretty diverse group and can be found nibbling on rotting vegetation at the

  • bottom of freshwater ponds -- and lots of other places you might care to look.

  • Or sometimes in our intestines.

  • Even though they look like single-celled blobs, they actually have more in common with animals

  • than single-celled creatures like bacteria or archaea.

  • And just because they're a single cell doesn't mean they don't have some cool tricks up

  • their sleeves.

  • For one, they can create temporary arms or legs

  • to help them move or feed.

  • They do this by extending and retracting blobs called pseudopodia from their tiny single-celled

  • bodies.

  • When moving, these pseudopodia grab onto a surface, and then the rest of the body contracts

  • to move in that direction.

  • When eating, the temporary limbs grab bacteria instead -- or whatever the amoeba wants to

  • munch on.

  • Then the food is engulfed by the amoeba's membrane and brought directly into the cell

  • through a process called phagocytosis.

  • For smaller particles, an amoeba can encase a little bubble of nutrients and surrounding

  • fluid through a similar process known as pinocytosis.

  • And it's this style of eating that leads to amoebas' second trick: dodging the immune

  • systems of larger creatureslike humans.

  • See, some amoebas can cause disease.

  • Like Entamoeba histolytica, which can cause pretty nasty intestinal problems and even

  • lead to death.

  • Instead of just feasting on bacteria, these guys have a fondness for human tissue.

  • They lodge themselves inside us, usually in the intestine, and nibble away at our cells,

  • taking tiny bites until those cells die.

  • This feeding process has yet another name: trogocytosis.

  • As well as getting a nutritious meal, amoebas pick up proteins from the outside of our cells

  • that they then wear like a mask to hide from our immune system.

  • Unlike what we know about VSPs, this disguise actually tricks the immune system into recognizing

  • the amoeba as one of our own cells.

  • That protection allows amoebas to travel around the body through our bloodstream and infect

  • other organs, like the liver.

  • But exactly how amoebas go from nibbling a chunk of cell to wearing some of the proteins

  • from that cell isn't yet understood.

  • Like, does the amoeba just stick the proteins on its surface somehow, or does it do something

  • to process them first?

  • Answering these questions could help us understand how they make us sick -- and how to stop them.

  • The third microscopic creature on our list has the potential to help us clean up our

  • oceans, rivers and ponds, and doesn't hurt us!

  • Yay!

  • Rotifers are aquatic invertebrate animals found in many places, including fresh water

  • and moist soil.

  • In fact, you might find some in your backyard if you look at some water from moss or your

  • gutter under the microscope.

  • And yes, they are animals, even though they don't look much like cats or fish or humans.

  • You can still pick out a basic animal body plan if you look closely.

  • They have a head, neck, trunk and foot -- and even an eyespot and toe.

  • Oh, and did we mention they wear crowns?

  • They're like royalty….

  • These little guys are filter feeders, meaning they suck in water from their surroundings

  • and pull out bits of organic matter to munch.

  • And their crowns are actually little finger-like parts called cilia that sweep water into their

  • mouths.

  • Their amazing filtering ability made rotifers the inspiration for a cyborg that cleans contaminated

  • water in one 2019 study.

  • The advantage of using tiny robots, instead of a stationary filter, is that they can move

  • around and mix the water up, which speeds up the clean-up process.

  • Which is important, especially if a contaminant like oil is putting wildlife in danger.

  • And yes, they're really cyborgs -- made of both living and artificial parts.

  • They're basically rotifers, but have had specialized microbeads added to their filtering

  • organs.

  • The so called self-propelled biohybrid microrobots, orrotibotsfor short, swim around and

  • sweep contaminated water into their mouths using their cilia.

  • Then the microbeads neutralize the bad stuff.

  • The researchers showed that the rotibots could successfully clean up E. coli bacteria, a

  • nerve agent, and heavy metals from water samples in the lab.

  • And they could survive in a range of environments like pools, ponds, or lakes.

  • That makes these rotibots a really versatile clean-up crew, because you wouldn't need

  • to design a totally different bot for different environments.

  • You'd just have to customize the microbeads to work on different contaminants.

  • The authors of the paper even suggest giving the rotibots caffeine to turbocharge their

  • swimming and clean water up faster.

  • Last on our list is a tiny green alga that's showing scientists how life on Earth evolved.

  • Volvox is a genus of green algae that clump together in spherical colonies made up of

  • anywhere from five hundred to sixty thousand individuals, depending on the species.

  • They're found in clean, warm, nutrient-rich ponds all over the world, and you might be

  • able to spot them with your own microscope in a bit of pond water.

  • In fact, some are big enough to see with the naked eye.

  • What's amazing is that those hundreds or thousands of individuals all coexist as a

  • single colony unit.

  • Most of them make up the transparent sphere that houses the colony.

  • These are called somatic cells.

  • Then there are a few larger cells on the inside that take care of reproduction.

  • This is about the simplest possible example of cells having specialized functions.

  • And that makes Volvox perfect for studying the development of multicellular life.

  • When an organism has only one cell, that cell has to do everything, from moving around to

  • finding food to reproducing.

  • But in multicellular organisms like us, those functions are split up between different types

  • of cells.

  • And Volvox's cousin Chlamydomonas makes for a great comparison.

  • It's also an alga, but a unicellular one.

  • In 2010, scientists sequenced the genomes of both and found that, on a genetic level,

  • the two were really similar.

  • The number of genes, as well as the number of different kinds of proteins those genes

  • coded for, were almost identical between the two.

  • Having almost the same set of genes shows they're closely related.

  • But how those genes are used accounts for the differences in what their cells can do.

  • In a 2017 study, scientists sequenced the RNA of Volvox carteri somatic and reproductive

  • cells.

  • RNA sequencing provides information about how genes are being expressed -- how the cell

  • is using its genome.

  • That let them see which genes are most active in each type of cell, that is, what jobs each

  • kind of cell does.

  • What they found was that more than half of Volvox's genes were expressed differently

  • in somatic and reproductive cells.

  • For example, in somatic cells, twenty-six percent of the most active genes were linked

  • with flagella -- little whip-like structures that help the cells eat and move.

  • But only two percent of the most active genes in reproductive cells were connected with

  • flagella.

  • And in Volvox, certain genes suppress the ability of somatic cells to reproduce -- leaving

  • that function to the reproductive cells.

  • In Chlamydomonas, reproduction can be switched on and off so that cells can alternate between

  • the two functions.

  • This shows that incredibly slight tweaks in how genes are expressed can make the difference

  • between a single-celled organism and one that looks a lot more multicellular.

  • Light microscopes might not be the flashiest models available.

  • Sophisticated instruments can use electrons or sensitive probes to visualize things practically

  • down to the atomic scale.

  • But don't discount the humble compound microscope!

  • The organisms you see through that eyepiece have a lot to teach us -- from unlocking new

  • vaccines to illuminating the origins of life as we know it.

  • Ever since the development of the first microscope hundreds of years ago, hobbyists and citizen

  • scientists have been discovering weird, wonderful, tiny things in drops of pond water.

  • In fact, we love this magical little world so much, we'd like to introduce our brand

  • new sister channel: Journey to the Microcosmos.

  • Every week, we'll bring you new, up close and personal looks at the microorganisms all

  • around us.

  • James Weiss creates all the incredible footage, set to music by Andrew Huang.

  • Oh, and it's narrated by me.

  • Journey to the Microcosmos is reflective, fascinating, and incredibly relaxing.

  • Check out the link in the description if you want to see more!

  • {♫Outro♫}

{♫Intro♫}

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