When it comes to why we spend our time  here together looking into the microcosmos,   I’m sure we all have our own reasons.

Maybe the mysteries of the algorithm lured  you here. Maybe you just like peering into a world that feels so distant from our own,   that feels full of creatures so different from us.

But…just how different are they…? We’re focusing today on a Journey  to the Microcosmos favorite: the ciliates, the single-celled eukaryotes  covered in hair-like structures called cilia. In our last episode, we ventured  into the murky depths of ciliate   history and what our studies on them  have taught us about, well, you know, them.

Today, we thought we'd be a little more self-centered and   explore what ciliates have  taught us about ourselves. Of course, just looking at ciliates, it’s  hard to find much of a resemblance to us. To start, they’re made up of just one  cell, able to carry out all their needs   with the organelles packed into  the confines of one membrane.

We, on the other hand,  start out as a single cell. But that single cell must divide over and over  so that the trillions and trillions of   cells it eventually forms can cohere into  different structures that become a body. Ciliates also have reproduction options  available to them that we do not,   like asexual reproduction where one cell  can divide and produce a clone of itself.

And as we talked about in our last video, some  ciliates also have two different types of nuclei. And during reproduction, those different nuclei go   through their own complicated process to  form the creation of the new ciliate— a process that certainly does set them apart from us. So, where are some of similarities?

You might be think, “Sure, there are different features, but at the  end of the day, we all have the same DNA.” And it is remarkable to look across  nature and remember that we are all   built out of a common code, a  shared path from DNA to protein. Except…ciliates throw a wrench in that seemingly  fundamental similarity too. Many ciliate species— including paramecium, blepharisma, and euplotes— use certain parts of their  genetic code differently from us,   deviating from the norms that are so common to so many organisms.

So if we can differ so fundamentally  from so many ciliates, how is it that   they have anything to teach us about ourselves? Well, for one, we share a home,  which means that we’re always   crossing paths with ciliates,  even when we don’t realize it. Our lives are built on ecosystems  that they help lay the groundwork for,   whether that’s through photosynthesis or  contributing to the food web or breaking down dead stuff or something else.

So learning more about ciliates helps us better  understand the way our own home functions. But ciliates don’t just intersect with us.   Watching them also reveals  the way they parallel us. And who better to explain this than  our own master of microscopes, James,   who has dedicated so much of  his life to watching ciliates.

James: Ciliates are just single cells, but  they behave like multicellular animals. They react to things, and watching them  kinda makes you think about free will,   because everything I am feeling is also a  reaction to a chemical compound in my body. Getting this chance to witness life  in a very pure, cellular level just made me develop this healthier habit  of trying to understand myself better.

Hank: What James is describing is in line with  a whole history of ciliate research,   where our ability to watch and  study these small creatures   enables us to better understand the  tiny, invisible parts of ourselves. For example, scientists have been studying the  way that paramecium swim for more than a century. And in the 1970s, these scientists  reported that the movement of paramecium was   controlled in part by calcium ions that travel  across the organism’s membrane and into the cell. Eventually, some of the same mechanisms and  molecules involved in that behavior were   found to be controlling the activity of neurons— transporting a pathway found in  ciliates to more complex creatures.

Another ciliate—tetrahymena—  has also made its own mark in   our understanding of ourselves.  You may have heard of telomeres. These are protective caps at the end  of our chromosomes made from repeated   DNA sequences that help ensure the essential  DNA does not get lost during DNA replication. With every replication, the  telomeres get shorter and   shorter, eventually they are  too short for the cell to survive.

Our first understanding of telomeres came in   the 1930s when two scientists who  were not working with microbes. One was Hermann Muller, who  was observing fruit flies. And the other was Barbara  McClintock, who was studying maize.

Over the next few decades, scientists were able to   expand their understanding of  telomeres and DNA in general. But techniques to work with DNA were  still quite limited compared to the   resources scientists have available to them now. So one of the major challenges  in studying telomeres was working   with the sheer length of the DNA  that is found in eukaryotes.

But when they realized tetrahymena  contained numerous minichromosomes,   they also realized they had the material  to more readily study how telomeres work. And they even found that the tetrahymena  telomeres worked in yeast cells too, suggesting   that there was something about telomeres that  seemed to be shared by a number of species. The work in tetrahymena also helped  scientists find the enzyme that   maintains telomeres, which is called telomerase.

There are so many aspects of this  work that could make it seem like   it’s just one of those fun ciliate  traits that scientists uncover. It’s a little funny cap on their chromosomes,  what could it possibly have to do with us? Well if you’ve heard of telomeres,  then you probably know the answer.

Our chromosomes have telomeres. And scientists eventually realized that  because of their rapid replication,   cancerous cells have shorter  telomeres than non-cancerous cells. So to survive, these cells often evolved to have more active telomerase enzymes.

In a 2006 paper detailing the  history of telomere research,   the scientists instrumental to their  discovery described the work as, quote, “pure curiosity-driven research.” They did not set out to uncover a mechanism that   lay at the center of how cancers  operate and might possibly be treated. They just wanted to look at something  cool they found in a ciliate. It’s hard to know exactly  what we want to make of that.

On the one hand, it is incredible  to look at ciliates and think, “wow, they helped us understand how cancers work.” But on the other hand, it’s hard to escape this  presumption that can accompany that sort of   statement, that we need some kind of justification  for curiosity beyond just the curiosity itself. But maybe that’s the whole point: that there is no curiosity of its own. Curiosity always exists in the context of  what drives it, and what it's made of it– just like James said, everything I feel is just a  reaction to a chemical inside of my body.

We’re just lucky enough to have evolved curiosity,   and we evolved it because it gave us  advantages, and so when we are curious we should no be surprised when it delivers results. And that definitely does not lessen my appreciation for it as one of  the very finest qualities of humanity. Thank you for coming on this journey with us as  we explore the unseen world that surrounds us.

The people on the screen right  now are our Patreon patrons. They are also people who I'm pretty  sure are chasing their curiosity. Thank you so much to everybody who  has ever supported this channel.

And if you want to join up for at  least the last little bits of this   channel existing because we are  going to stop making videos soon, you can do that at Patreon.com/JourneytoMicro. If you want to see more from our  Master of Microscopes, James Weiss,   you can check out Jam and Germs on Instagram. And if you want to see more from  us, please go explore our archive.

There are so much good stuff on this channel.