Cordyceps in Real Life? TXST Biologist on the Fungi Behind The Last of Us

David Rodriguez, Ph.D., researches ecological, evolutionary, and anthropogenic processes that influence biological variation, specifically diseases of amphibians and bacterial symbiont diversity.

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Name: David Rodriguez, Ph.D.
Title and Department: Associate Professor, Department of Biology

This interview was taken from a Faculty Experts video and an upcoming episode of Enlighten Me featuring Rodriguez. It has been edited for brevity.

Cordyceps was popularized by The Last of Us. What is it, and should humans be worried about it?

DR: Cordyceps is a group of fungi that specialize in and infect insects. The species that became popularized is Ophiocordyceps unilateralis. People became interested in studying it because it controlled the behavior of insects to propagate infection, and they termed these ants as “zombie ants.” When I go to Ecuador to research a fungus that infect frogs, I see lots of cordyceps in the forest infecting months, spiders, and ants.

It's unlikely to ever infect humans because it has evolved to specifically infect insects. They have a simpler immune and nervous system than humans do. The fungi that can cause infections in humans are mostly opportunistic and affect immunocompromised patients. Unless the world becomes completely immunocompromised, it’s unlikely that fungi will take over and affect our central nervous system in a way that controls our behavior. So, we’re safe.

What happens when cordyceps infects an insect?

DR: It all starts with the spore, which comes from a structure called the sporocarp. It’s where the spores develop and where it disperses from. When an ant encounters the spore, it will attach to its exoskeleton. Once its inside, it starts growing hyphae, which you can think of like little roots. It takes the nutrients from inside the ant and then begins changing the behavior of the ant through metabolites from its cells. The ant will then go clasp onto the bottom of a leaf and die. Once the fungus runs out of food, it will generate a new sporocarp and release more spores. The ants become a propagation mechanism effectively.

Where can people encounter fungi in Texas?

DR: There are species in North America and all over the world. The fungal kingdom is a huge group with lots of diversity. We take students in mycology classes out to the ponds next to the J.C. Kellam Building because there’s lots of water and rotting wood. You’ll find common earthballs and different colored mushrooms all over the place.

How does fungi infect amphibians?

DR: I study fungi that kill frogs, Batrachochytrium dendrobatidis. Most people think of fungus as sessile, but there are some that are motile. The spore will swim through the water toward a food source, which in this case is the frog skin. Amphibians use their skin to respire. Once you start affecting the capacity for osmoregulation through the skin, then you start affecting the physiology of the frog, which can lead to a greater susceptibility to predators or death. There have been populations that have been completely wiped out from regions because of this fungus.

What are the beneficial components of fungi?

DR: Fungi do amazing things for us. Most of us wouldn’t be here without fungi. The Penicillium species, which is where penicillin came from, is responsible for saving millions, if not billions, of humans from infections. Before penicillin, if you were to get a major cut, you might likely die of infection. We also use fungi to produce insulin for people who are diabetic.

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