This episode was sponsored by Blinkist.

Blinkist puts all of the need to know information from thousands of nonfiction books and condenses them down into just 15 minutes and you can go to blinkist.com/microcosmos to learn more. Recently, we did our first ever Journey to the Microcosmos livestream.

Some of you may even have been there, whether that’s because you wanted to see the microbes that James, our master of microscopes, was showing live from his own microscope, or because you wanted to see our faces. To be honest, we’d understand if you were there mostly for the microbes, but whatever the reason, thank you for joining us. The real highlight though for all of us was a moment that combined the best of microbes and faces.

It is this moment right here, that look on James’ face when he realized that something very exciting had just appeared on the screen. Here, I’ll just play it and you can experience the excitement again in real time. The thing that had James so excited was that green, glow stick-looking ciliate called Spirostomum semivirescens, it’s a large ciliate he had been working to find for over three years, and it just happened to show up during our livestream.

His mentor Professor Genoveva Esteban was watching the livestream from the UK, where she works at Bournemouth University. And when the moment of recognition hit both her and James, she texted “omg” followed by approximately 14 exclamation points. Look, 2021 has been a strange year, and the pandemic has led to lots of changes in how we share and talk about things.

But there’s some joy to be had in the fact that we could share this moment as a community spread all around the world…all of us peering through a microscope as James guided us through what we were seeing. But of course, the real question is why were James and his professor so excited? Well, there are currently eight known spirostomums in the world, their bodies all long and contractile and twisty.

Some of these specimens can grow as much as 4 mm in length, making them both visible to the naked eye and potentially easy to confuse with worms. And while some of these species are abundant, Spirostomum semivirescens has been a much rarer find. It’s surprising, when you look at it.

After all, this is a 2 mm long, bright green ciliate slithering through a field of smaller organisms and debris. It’s just so glaringly there. How could it be difficult to find?

Well, according to the reported observations, pretty difficult. There’s a record from Germany dating back to 1852. And in 2009, Professor Esteban and her team recorded their presence for the first time in the UK.

In 2015, they followed that up with a study of Spirostomum semivirescens found in two Swedish ponds: one in farmland, and the other in an ancient forest. Now, it’s hard to pin down exactly why this species might be so rare. Some microbes are just like that, probably because they’re particular about what kind of light or food they like to have around them.

The thing about being rare though is that sure, it might take a while to find a spot where the organism likes to live. But once you find their home, they can turn out to be fairly abundant. We talk about ponds like they’re one big habitat.

But for microbes, they’re actually many, many, many habitats stacked on top of and below and around each other, with fuzzy boundaries defined by chemical gradients and temperature changes and physical entities that create many different types of homes that suit many different types of organisms. And so finding organisms like Spirostomum semivirescens can sometimes be a matter of sampling many different places, or it can be a matter of sampling the same site over and over again. Either way, microscopy rewards the patient and diligent.

And the rarity of Spirostomum semivirescens is made all the more interesting because of its size. There’s this idea in microbiology, maybe you’ve even heard of it: “everything is everywhere, but the environment selects.” That phrase was coined by the Dutch microbiologist Lourens G. M.

Baas Becking in 1934. Becking himself was drawing on the work of another Dutch microbiologist named Martinus Beijerinck, who had observed that using different culture conditions allowed him to isolate different types of bacteria from his samples. When extended beyond the confines of a lab culture, the premise is this: microbes are tiny.

Like super small, right? But they’re also able to form very large populations, growing massive in number, if small in size. And as a result of their small size and large populations—not to mention their ability to form protective cysts— it is not hard for microbes to disperse and spread.

There are many of them. They can stick to the legs of ducks and turtles. They can blow on the wind.

We find the same species of microbes all around the world. They find it easy to move around. But of course, not everything is actually everywhere.

How could they be, when there are so many different types of places to be. Well, that’s where the second half of the hypothesis comes in: “but the environment selects.” The microbes may disperse easily and spread widely, but what survives is the result of the many environmental factors they land in. But of course there are limits to this.

Microbes find it easy to move around, kangaroos do not. There’s a size at which it gets more difficult to be everywhere Spirostomum semivirescens’s large size makes it an exciting organism to consider against this idea of everything being everywhere because it’s like pushing the limit of what makes a microbe easy to disperse. And that makes the discovery of the species at distant ponds all the more compelling.

But while “Everything is everywhere, but the environment selects” may just be a single sentence, the debate it has inspired has spanned many decades worth of research papers. There are other scientists who have reported bacteria that appear to be rendered distinct by their location, making their biology a function not just of environment, but of whatever history separated them from other similar species. The nuances of how to think about and interpret “everything is everywhere, but the environment selects'' is itself a reflection of just how remarkable microbes are, and also the dialogue that shapes science over long periods of time.

And while our Spirostomum semivirescens cannot bring the conversation to a close, we are excited to have been able to interrupt it for a moment, with just a little bit of new information. Thank you for coming on this journey with us, and also to those of you who were there for this moment on our journey as we explore the unseen world that surrounds us. So how’s that 2021 reading list coming along?

You finding yourself distracted? Maybe just too busy to sit down and read all of the books you’ve been meaning to get to? Thankfully, Blinkist is here to help you learn new things in just a little bit of time!

Blinkist highlights the most important insights and need-to-know information from nonfiction books and condenses them down so that you can either read or listen to them in just 15 minutes. And if you’re looking to learn even more about wiggly, weird things that live in water, you might want to check out The Book of Eels by Patrik Svensson, which is available on Blinkist. Seriously, eels are very weird.

We’re still now even 100% sure where and how they mate. You’re going to want to learn more about eels. Whether you’re interested in science, history, or business, Blinkist has something for you in the 3,000-plus non-fiction titles in their library.

And if you’re one of the first 100 people to sign up today at Blinkist.com/microcosmos, you can get free unlimited access for 7 days and you’ll also get 25% off if you decide to get a full membership. We also of course need to thank today, and also every other day, our patrons on Patreon. You’re seeing some of their names on the screen right now, and without them, this show could not exist.

So, if you like this show and you want to help us continue making it, you can join all of those amazing people at patreon.com/journeytomicro. If you’d like to see more from our Master of Microscopes James Weiss, you can follow him at Jam & Germs on Instagram And if you’d like more from us, there’s always a subscribe button somewhere nearby.