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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 overhead 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, but… isn’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 creatures… like 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, or “rotibots” for 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?}.