The processes behind lichen — the poster child for symbiosis — misunderstood for more than a century, until now

EDMONTON — Our understanding of the marriage of fungus and algae in the formation of lichen is being upended by a University of Alberta research team whose work is rewriting the biology that introduced symbiosis to the world.

Symbiosis was discovered in the 1860s by a Swiss botanist who was able to determine that lichen was not one thing but rather a symbiotic partnership of a fungus and an alga. 

What scientists thought then — and for the next 150-plus years — was that the alga present photosynthesizes and produces sugars that the fungus takes up and uses to grow and fuel the lichen, in exchange for the structure and protection the fungus provides.

“Lichens are literally what high school biology teachers use to teach symbiosis,” says Toby Spribille, professor in the Faculty of Science.

He explained If this symbiotic relationship is as the textbooks suggest, then the genome of the fungus getting a sugar subsidy in exchange for protection, over the millions of years of evolutionary time, would lose the ability to make enzymes to break down more complex sugars.

Instead, what Spribille’s group found was that the genomes of lichen fungi retained all kinds of different abilities to break down complex sugars, including some with an enzyme repertoire that closely resembles fermenters used in biotechnology.

Spribille explained what he thinks is happening is that the sugars being provided by the alga are not used to grow the lichen, but instead are saved up to preserve cellular content when lichens dry out, which they do once a day.

“This calls into question the entire basis of lichen symbiosis,” he says. “New discoveries happen with symbiosis all the time, but the exciting thing here is this is the symbiosis that got it all started.”

To speak with Toby Spribille about his study and to listen too one of best analogies you will ever hear, please contact:

Michael Brown
UAlberta media strategist
mjbrown1@ualberta.ca