Koala genome study offers clues into marsupial's toxic diet and fight against chlamydia

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Koalas are facing threats like habitat destruction and disease. But thanks to a new project that mapped the genome of the cuddly marsupials, scientists say they have new information that might help conserve koala populations. 

This week, researchers published their findings in the journal Nature Genetics. The work was five years in the making and involved dozens of experts from around the world.

To tell us how that might actually help the koala populations, As It Happens guest host Robyn Bresnahan spoke to wildlife forensic scientist, and lead author of the paper, Rebecca Johnson. 

Here is part of their conversation.

I think the koala is largely known for being cute, cuddly — but it turns out they are living a pretty tough life. Can you tell us about some of the challenges they are facing?

They definitely are known as being cute, and maybe cuddly, although those claws are pretty fearsome. The genome has given us brand new insight into the understanding of koalas.

They live in the trees and they live on just a few species of eucalyptus as their primary food source. Even though we have hundreds of species of eucalyptus here in Australia, they really only eat about 20 of them. 

The genome has shown that they have this amazing ability to detoxify because eucalyptus is basically poison. If we ate it to the same level of koalas, we would probably die. 

So how are they able to eat this poison and not die?

We found in the genome that they had a couple of big expansions of this particular group of metabolic enyzmes.

These enzymes are very important for life. Practically every living organism has them from bacterial to big multi-cellular organisms like us.

But koalas seem to have many more of these detoxification enzymes for this one particular group than any other species we were able to compare it to.

We also found, from looking at different koala tissues, that they are particularly expressed in the liver, which is exactly where we would expect them to be.

I also understand that the koala also has a bit of a chlamydia problem?

Yes, unfortunately it's one of the threats that they are facing. They're a vulnerable species here in Australia, and that's for a range of reasons, but chlamydia is certainly something that ravages quite a few of the populations.

They get it in their eyes and they also get it in their urogenital tracts. So it can make them blind if it's in their eyes or it can make them sterile if it's in their urogenital tracts. You can imagine what effect that would have on an animal in the wild. So if they're lucky they can be taken into care and treated for that chlamydia. 

Finding these detoxification abilities that they have actually explains a lot about how they are treated for chlamydia because when they are treated they're given these massive doses of antibiotics. They are often given antibiotics for 30 days in a row.

That might treat the chlamydia. So clearly their ability to detoxify is having effects on this type of veterinary care as well. So we're hoping that the genome is going to advance and improve the way that these kind of diseases are treated.

This entire genome project has been posted online. The public can see it. What are you hoping that researchers who look at this information will try and do with it?

The sky's the limit almost, once you have a genome. 

For the human genome, for example, 20 years after it was sequenced, we are still discovering things about humans. The therapeutics and the knowledge that we get in the ability to treat things or understand things continues to improve. So we're hoping that will be the case for koalas.

What new appreciation do you have for koalas now that you have completed this project?

I admire how much they sleep.

They sleep up to 19 hours a day and they spend the rest of the time eating — and maybe a few minutes a day moving between trees. So they have a really interesting breakdown of activity.

I have to say, they're pretty chilled out animals.

Written by Katie Geleff and John McGill. Produced by Katie Geleff. This Q&A has been edited for length and clarity.