16 May 2017

Meet the mycologist: Pepijn Kooij

Find out what Kew’s mycologists are working on in this special Friends Week Q&A. Today, Pepijn Kooij tells us about his research on fungus-growing ants.

Pepijn Kooij

By Dr Pepijn Kooij and Kew Foundation


What is your job title and role at Kew? 

My name is Pepijn Kooij and I’m an early career research fellow. I’m doing my own comparative research, looking at the different fungal species associated with fungus-growing ants. 

What’s your favourite specimen in Kew's Fungarium? 

My favourite specimen in the collection is Leucoagaricus gongylophorus, which is a mushroom that has come from an ant colony. It’s very rare; normally these fungi don’t grow any mushrooms because the ants actively transfer the fungus in order to create new colonies, and that way the fungus is passed on to the next generation. The specimen in the Fungarium comes from a laboratory colony grown here in the UK. 

How do you collect fungi? 

There are a lot of different ways to collect fungi, but for my current research, I collect samples of ant colonies that grow the fungus Leucoagaricus gongylophorus. You can see in the photo of the ant colony; there are the ants themselves, the pieces of leaves the ants have cut, and the white fungus that ties everything together. The fungus degrades the plant material the ants bring in, and then the ants eat the fungus. 

To collect a sample it depends on what species you’re looking for, but for any of the leaf-cutter ants we tend to look for younger, smaller colonies. You can tell how old a colony is by the number of entrances; one entrance in the first year, two in the second, between three and five in the third, and beyond that it becomes impossible to tell! 

To collect your sample, you dig a small trench a short distance from the entrance and then you slowly dig towards the fungus. You can then collect it with a spoon and transport it to the laboratory. It’s useful to end up with the queen ant because then you can set up a new laboratory colony. One of my goals is to set up some colonies here at Kew for my research. Leaf-cutter ants can grow fungus gardens the size of an American football, but the smaller species tend to grow their colonies in walls and they’re very small. To collect samples of these we use teaspoons! 

One way to find the ants in the first place is to bait them with biscuit crumbs. When the ants come to collect the crumbs, you follow them back to the colony. 

What project are you working on at the moment? 

The main focus of my research here is on the fact that the fungus Leucoagaricus gongylophorus doesn’t grow these mushrooms (fruiting bodies). How and why are they kept sterile? Occasionally we have seen mushroom growth, but it’s rare, and often only when the colony is dying. I think there are three different possible causes. 

The first theory is that this fungus is actually polypoid, which is often very beneficial because they tend to grow bigger, more diverse enzymes to break down plant material. However, polyploidy also causes problems; for example they can’t divide chromosomes well, and that in itself can cause issues. 

The second theory concerns the influence of the ants themselves. We know that when mushrooms start growing the ants will attack it; this can be described as an epigenetic influence on gene expression, meaning that there are environmental factors which can influence genetic expression. In this case the ants can potentially turn particular genes in the fungus on or off. That’s the theory anyway. 

The last theory, which I’m working on at the moment, is the possibility of a viral influence. It’s been found that growers sometimes struggle to grow extra mushrooms, and the reality is that there was a virus causing the fungi to become sterile. That would be perfectly fitting for my study. It would also be perfect for the ants as they could monitor the fungus, using the virus to prevent mushroom growth. 

There’s always a struggle for balance with mutualism; even though they may make each other stronger, one species will always want greater benefits, causing a constant struggle to get the upper hand. We have some preliminary data showing evidence of viruses in the fungus, and I’m now growing more fungus so that I have enough material to extract the viruses and sequence them. I can then see which genes are involved and what they do, potentially adding another organism to the system.  

Kew Friends Week 

This Q&A was written especially for Kew Friends Week. During Friends Week, we celebrate our Friends' invaluable support to both the Gardens and Kew's vital science and conservation work, with a week of exciting content and activities exclusively for Friends of Kew.  

Find out more about becoming a Friend of Kew