A Slime Mold Called Le Blob

“Le blob” is what French researcher Dr. Audrey Dussutour calls the creatures she grows in her lab. She drew inspiration from “The Blob,” a 1958 American horror movie starring Steven McQueen about a giant alien from space that eats people and grows uncontrollably. It reminded her of her slime molds, minus the eating people part. Oh, and being an alien. Well, some folks have thought slime molds were aliens, but I’m getting ahead of myself. After Dr. Dussutour started using the name “le blob” for her slime molds, it caught on so much that now (almost) everyone calls them “le blob” or “the blob.” Naturally, there are always naysayers—some folks thought these slime molds should be addressed by their scientific name, Physarum polycephalum. But Dr. Dussutour says, “No one remembers that name. Everyone remembers the blob!”

So, get ready to learn about the blob! I had the absolute pleasure of interviewing Dr. Dussutour and learning about her work with slime molds. She explained her research, told some ridiculous and funny stories about these fascinating creatures, and shared about her ventures into writing a book, filming a documentary, and interacting with the public in her Facebook group about slime molds. I hope you enjoy my interview with her.

Question: Tell me a little bit about who you are and what you work on.

Answer: I started out working with ants and then worked with slime mold during my postdoc in Australia, where I studied their nutrition. Then, I took a position as a researcher in France at the Centre National de la Recherche Scientifique (CNRS) and brought the slime mold along. A student of mine wanted to work on slime molds after reading my paper on them, and I said, “I don’t work on slime molds,” but then we started again, and I really liked it, so we continued.

Question: What do you like about slime molds?

Answer: They are easier to work with than ants. You can have as many as you want, you can clone them by tearing off pieces, they never die, and you can run a lot of replicates—it’s really good to have a model that you can run a lot of experiments. With ants, you have to collect several ant colonies, and it might be difficult to find them in the field. But with slime molds, you can grow them, so you can have as many as you want, and they double in size every day. Also, you can put them in a dormant stage when you go away, so you don’t have to have someone to feed them for a while. However, you do need to feed them every day when you work with them, and they can escape and crawl around.

They are quite fun and simple organisms, but at the same time, they are kind of smart. You can study decision-making and learning, even if they are single-celled organisms. They also can interact with each other: they leave cues when they move around, and the other ones can track these cues. They are very good at following gradients in their environments. Ants have a central nervous system, but slime molds being unicellular have no central nervous system. 

It’s just a giant cell, with a ton of nuclei—it’s like a colony of nuclei.

Question: What is a slime mold exactly?

Answer: First of all, there are two types, cellular and acellular. People always confuse them. They share the same name, but they have nothing to do with each other. We are working on acellular slime molds. They both belong in the kingdom Amoebozoa. They are super different, but that’s like saying we are all animals. The common point is that they both start their life as amoebas. The cellular slime molds, sometimes called social amoeba, are far more studied than acellular slime molds. They are super small and cannot be seen with the naked eye, but they can aggregate and form a multicellular slug. Joan E. Strassmann (Nature) showed that they have primitive agriculture with bacteria. 

But this is an interesting question. In the 70s, people were fighting over what slime molds were because some were saying they were fungus, and some were saying they were animals. But since the 90s we’ve known what they are. They belong to the amoebozoa kingdom, the myxomycetes class (also called slime molds), and the species is Physarum polycephalum. They are very easy to rear in the lab.

Physarum polycephalum is a giant unicellular organism. It can reach up to 10 meters squared. It starts its life cycle as a spore, which was why they were thought to be fungi. The spore germinates and becomes a tiny amoeba. Then, in liquid medium, it grows two flagellates. Reproduction happens when two cells fuse and form an amoeba. It then goes through a lot of mitosis and forms a giant cell. This giant cell distributes nutrients using a sort of circular system, which looks like a network of veins. The cytoplasm and nutrients move fast at 2 m per second. The veins are surrounded by fibers of actin and myosin, the contraction of these fibers push the cytoplasm and allows the cell deformation and movement. 

But a slime mold doesn’t crawl super fast, maybe 1-4 cm per hour.

They usually live in the shadows because they fear the light. You find them in the forest on old bark and leaves on the ground. They eat mostly mushrooms or bacteria. When we feed them, though, we give them oat flakes (Quaker oatmeal). Someone in the 60s figured that out, and now everyone does it all around the world.

Slime molds are quite famous in the US because, in the 70s, a woman in Texas found one—a dog vomit slime mold (Fuligo septica)—and thought it was disgusting, so she tried to kill it. She used a garden hoe and smashed it, but the next day it had doubled in size. She tried to poison it with things she found in the garage, but it only changed color and was still fine. She was scared, so she called the firemen, and they sprayed it with water, but it continued to grow. She then decided to call the police, and they shot it. The slime mold continued to grow, but then it simply disappeared because, in fact, it went into sporulation. But she didn’t know that. And so at the end of a report in the Washington Post (see below), they said that she was visited by an alien. I used it in the intro to my book because I found it very amusing.

People really like slime molds because they are big and yellow and people don’t understand what they are. It’s weird that you can actually grow to like a slime mold—you can get attached like a pet. I’m even sad when they get sick. When my slime mold gets an infection, I’m like, “oh poor baby.”

Question: How is slime mold different from fungi (actual molds)?

Answer: They were not categorized as fungi in the end because of the way they eat. Slime molds eat by phagocytosis: they swallow big stuff, for example, bacteria and yeast cells. Fungi, eat small stuff by pinocytosis. Also, slime molds move a lot in comparison to fungi. Fungi grow, but they don’t really move. Slime molds crawl around.

One person, Anton de Bary, was sure it was an animal because it was predating on bacteria and moving around. He thought it was like an animal but a very slow one. Lindsay Olive was the first one to say that they might be protists and not fungi.

The ways they are similar, though, are in the way that they reproduce using spores.

Question: What are the big-picture reasons for studying slime molds or the larger implications?

Answer: Because you can study learning processes, which are restricted to animals usually. It’s thought that a central nervous system is needed to learn and memorize. But some authors showed that learning is possible in plants, so they thought, well maybe you don’t need a central nervous system, you need only multiple cells. 

Now, we are showing that slime molds can learn, so you don’t need multiple cells, either it seems. It’s like we are pushing the emergence of learning further away in time.

Now, we are trying to characterize the mechanism of learning. Slime molds can transfer information from one to another—they can teach each other something. For example, usually they hate salt, but you can teach them that it is safe and they can ignore it. Slime mold habituated to salt can fuse with naive slime mold and tell its mate that salt is safe. We want now to know what they are transferring. 

We are asking whether cognitive abilities are restricted to animals or if we can find some cognitive abilities in slime molds. Some call it “primitive cognition” or that perhaps we can find the “ground floor” of cognition in these types of organisms. But we’ll see.

Question: What is difficult about studying slime molds?

Answer: To convince people that they are interesting. It’s very easy with your family or a general audience. People love them. But scientists, in fact, not so much. They think they are not the best model to study because they are very particular. They say, “perhaps you should use another cell system that is better known.” It’s difficult to convince people it is a good cellular model.

Question: What is your favorite thing about slime molds?

Answer: I think my favorite thing is that they always surprise me. I initially thought they would be very boring, but they are not. They always do something that you don’t expect. 

And I really like the way that when you want to force them to do something, they just say no. They escape the Petri dishes and go away. 

I like the way that they interact. When we stress them, they always find new ways to avoid it. They are funny organisms.

Question: Do you have any specific stories of when they surprised you?

Answer: The worst story I have is the one I tell in my book. One day, I couldn’t come to the lab to feed them, and I had a lot of slime molds. At that time, I did not have chambers, and I had them on shelves, so they escaped.

I was used to them escaping, but this time because I had so many, they escaped and fused with each other and became a very giant blob. And they crawled on the wall, and I found them on the ceiling. It was disgusting. 

When I arrived, I saw that the Petri dishes were empty, but they couldn’t have disappeared completely. They are easy to track because they leave mucus. So, I could follow the track, and I found them on the ceiling. They were looking for some food, I guess.

Question: What color is the mucus?

Answer: It’s completely translucent. It’s kind of a ghost because it’s exactly the same shape of the slime mold. They just remove the cytoplasm and leave this mucus. 

And so they leave behind exactly the shape of the veins and everything, but it’s completely translucent. 

It’s amazing. And Chris Reid, a colleague of mine, showed that they use this mucus as an external memory. So when they navigate, they avoid this mucus because it informs them which part of the environment they have already explored.

Question: Are they harmful to humans? Can we touch them?

Answer: Don’t think so. We touch Physarum polycephalum all the time in the lab. I think they secrete stuff to paralyze their main predator, slugs. (They get eaten by slugs). Recently we made a documentary on slime molds, and we were filming them in their natural environment. We noticed slugs would eat and then stop and get completely paralyzed. And the slime mold would crawl on top of the slug and start eating the mucus on the slug. Then, suddenly, the slug would wake up and leave again with a piece of slime mold on their back. Nice way to travel using these slugs. I think perhaps they have a toxin they can secrete, but, for us, it’s harmless we touch them every day, and we never feel anything. 

Question: You published a book called Le Blob, can you tell me about it? Will it be available in English?

Answer: Not yet. Most of the book would work in other countries, but some parts of the book are specific to France, so I would have to change those parts for translated versions. 

It’s about the blob, being a researcher, and being a woman in science. I tell about slime mold, of course, but also about my life as a researcher, how I became a scientist, and how research works. I also tell about the way we do science and how we share our discoveries, I explain things such as impact factor, the struggles of finding a position and looking for funding, how if you get married it gets complicated, the constant pressure, the fact that you don’t have a normal day, that you work on Sundays, that you work during the night because maybe your colleagues live in Australia or you have a deadline coming, and how we have a responsibility to students. 

Some people, after reading the book, are surprised. They always imagine that a researcher is doing experiments on the bench all day, and now they realize how difficult it might be.

Question: Can you tell me a little bit about the film?

Answer: We adapted the book for a documentary that will be released in the US. It’s called The Blob: A Genius without a Brain. We traveled around to the US, Canada, Japan, UK to meet all of the slime mold researchers. In fact, it’s not just about slime molds because we visited people working on plants and other kinds of intelligence too. But, of course, it is centered on the slime mold. 

We traveled around and pushed for the idea that science is not just about applied research and innovation. It’s also about curiosity. It’s about trying to get interested in a very weird organism because we just want to know how it works, not because you want to make money out of it. It’s really nice because when we went to see Toshiyuki Nakagaki, who studies slime molds in Japan, and he has this really poetic way of seeing science—that sometimes we just have to stop and let nature overcome us and wonder about its complexity. So, the documentary is about intelligence when you don’t have a brain, and also about the scientific curiosity that enlivens researchers.

Question: When will the film be released?

Answer: It will be released at the International Festival of Scientific Movies in Paris, France in October 2019. After that, it will be on TV in January in France, and for the US, it will be later, maybe the end of next year.

Question: What are you most excited about coming up?

Answer: The blob is entering the National Zoo in Paris. The zoo will introduce five new species for this big Halloween event. 

It’s so cool because it’s not even an animal and it gets to be in the zoo!

It was cool because I had a kid send me an email and said he went to the zoo to see the blob, but it wasn’t there yet because it was arriving in October. Me, I went to the zoo because of the elephants. I think it’s good to get kids interested in such weird organisms. 

Usually, people are disappointed that it’s not moving. But I have to explain that it moves so slowly that you can’t see. But we have videos we can show them. And it’s good because they can leave with a piece of slime mold. You cannot leave with an elephant.

In France and the US, you can actually buy slime mold on the internet from Carolina Biological. When I wrote the book, I never thought that people would like slime molds and would like to have them at home. So, I never thought about adding a section about how to rear them. But afterward, I got emails from people saying, “I want to have a slime mold at home.” So, I did this tutorial online on YouTube (If you are on a computer, you can turn on subtitles in your language if you don’t speak French). I got so many questions, and with the video, it’s really easy because I just send the link. And so now people can buy slime molds, and they have this tutorial on how to rear them. 

I never realized that kids would be so into it. They experiment with a maze and send me pictures. And so I have this Slime Mold Facebook Page for the general public, and I interact with people a lot. 

It’s also a bit of citizen science. Once, a dad told me that his son actually found something interesting. That if I spray a substance called colloidal silver (silver in very tiny concentration in liquid) on the oat flakes (oatmeal), it prevents infection. So, we actually use that now. 

Question: Is there anything we didn’t cover that you feel is important?

Answer: We are moving into microscopic research, rearing “tiny” slime molds, also called microplasmodia (the plasmodium is the vegetative stage of Physarum polycephalum, it can be less than 1mm square (microplasmodia) or up to 10-meter square (macroplasmodia). So, we are doing real microbiology ;-). And they are funny because they are very frazzled. They don’t have veins yet, so it is super exciting because when you watch them, they move in all kinds of directions. They are very funny.

Question: What are you hoping to find studying them at this stage?

Answer: So, we just wanted to see if they could learn at this stage. My master’s student Julie Delescluse studied them for one year and found quite cool stuff about learning at this stage. But they are very difficult to analyze at this stage because they are moving all sorts of directions. We don’t really understand what is happening. So, we are working with some people who are doing machine learning to try to analyze what they are doing. We are not sure yet if they are learning or adapting. We have to test various criteria to be sure that what we are seeing can be called learning. If they learn at this stage, on this little thing, we can do microscopy and better understand the mechanisms supporting learning. With the giant one, it doesn’t fit under the microscope. It’s too big.

Question: Do you have any resources (books or papers) you would recommend?

This post contains affiliate links — see my disclosure policy.

Answer:

• Acellular slime molds –
  • Myxomycetes: Biology, Systematics, Biogeography and Ecology – Carlos Rojas Alvarado, Steven L. Stephenson. (BOOK)  Dr. Dussutour notes that this book can be difficult to read because some chapters contain very intense molecular biology, and that it is good for researchers, but that the history section is interesting.
  • Reid, C. R., & Latty, T. (2016). Collective behaviour and swarm intelligence in slime moulds. FEMS microbiology reviews, 40(6), 798-806. (REVIEW ARTICLE)
• Cellular slime molds – 
  • The Social Amoebae: The Biology of Cellular Slime Molds – John Tyler Bonner (BOOK)

Key Takeaways:

-Two distinct types of slime molds exist, acellular and cellular, and Dr. Dussutour studies the acellular Physarum polycephalum aka Le Blob
-The blob is one giant cell containing many nuclei that can crawl around and explore
-Intelligence is found in very primitive organisms without brains, even the blob
-Blobs can teach each other things by fusing and sharing information, and they keep track of where they have traveled by leaving mucus behind
-You can buy your own blob and grow it at home

To learn more about Dr. Dussutour and her research, you can visit her website and follow her on Twitter and on Facebook. Make sure you go watch this video on her Facebook page.

P.S. Be on the lookout when you are in the woods because, if you are lucky, you can happen upon a slime mold! They are quite a thing to see. Check out the photo in this post of a slime mold I saw this past year.