In case you ever think that biology is simple, easy, or well understood, take a quick look at a 959 cell organism called C. elegans. It’s a small nematode (a worm) that usually lives in soils and rotting vegetables and it’s a fantastic model organism, meaning we can study it easily to learn about our own biology. You would think that an animal with less than 1000 cells that has been researched for over 50 years would be reasonably well understood. This is true compared to other animals, but our understanding is not nearly complete.
To start, here are some cool things we do know about C. elegans:
- Every nucleotide of their DNA. They were the first multicellular organism to have their entire genome sequenced.
- Something about the function of around 4,000 genes: C. elegans have approximately 20,000 protein-coding genes, and from experiments and educated guesses, researchers can study the function of these genes.
- Every cell division of their development from a single fertilized egg to a fully developed adult.
- The connections between neurons. C. elegans was the first species to have a complete nervous system wiring diagram.
The reason C. elegans has been the subject of so much research is not just that scientists think worms are cool (although they do think worms are cool). They are an excellent model organism for several reasons. First, all the reasons my mom wanted me to have a pet fish instead of a dog: C. elegans are small, and we can fit a lot of them in a limited area. They eat bacteria, which are also small and easy to grow. They have short generation times and produce many offspring. But unlike fish, most C. elegans are hermaphrodites: they can self-fertilize and produce a whole population of little wormies from a single organism.
But it’s just a worm, so how can we use it to study human biology? I’m glad you asked. C. elegans are animals and have a lot of the same biological systems that we do including a simple nervous system, muscles, digestive system, and excretory system (for getting rid of waste).
I first learned about C. elegans last fall when I interned at a lab at Hanyang University. What made me excited enough to write a whole Quest article about these worms as model organisms is that they’re just COOL. They are very tolerant of environmental variations like temperature. They can even be frozen to pause their life cycle without killing them (I can’t be frozen, I’m cold in Berlin when it rains). They will eat most kinds of bacteria and grow on almost any surface like agarose gel, soil, liquid, or even plastic. You can poke them, squish them, shake them, and they remain relatively unaffected. You can even pick them up from one plate and transfer them to another and they will continue happily living their life. You can see them through a light microscope and watch them wiggle around, eat, lay eggs, and interact with other individuals.
They are also easy to manipulate genetically. It’s usually very tough to manipulate gene expression in organisms — opening a glass jar with oily hands tough. Gene expression controls most of organismal development and response to the environment. Usually, to examine a gene you have to mutate it, which is often inefficient and ineffective. But C. elegans researchers can use RNA interference (RNAi) to effectively silence genes just by feeding certain bacteria to the worms. That would be like if eating genetically modified tomatoes turned off one of your genes (though let’s be clear, RNAi is not that simple in humans, and genetically modified tomatoes do not mess with your genes).
Here’s the positive feedback loop of research: we know a lot about C. elegans, so it is easier to learn more. Now that we understand more, it’s easier to keep learning. Flash forward: we know a lot about a pretty random little nematode that doesn’t have a real impact on us, our food, or our environment. But people still spend their entire careers studying them. This worm was even the subject of a Nobel Prize in 2002.
If all this worm talk is creeping you out, don’t worry; C. elegans are benign to humans. In fact, they can’t even grow at body temperature so they can’t live on or in you (unlike bacteria, my other favorite tiny life form to talk about *rubs hands together*). But know that a lot of what we understand about your genes came from studying C. elegans.
NS144: Genetic Blueprint to Organism had a “Next Top Model (Organism)” costume contest. This group dressed up as a mutant worm called “bag of worms.” These worms cannot lay eggs but can still self-fertilize inside the hermaphrodite parent. This leads to the baby worms hatching inside the adult and then eating their way out. The balloons in this group’s costume represent baby worms coming out of their mother.