Lichens and Yeast

common orange lichens

Lichens seem to form a three-way partnership involving fungus, an algae and yeast.

The lichens are the perfect example of symbiosis. After 150 years of taking the organisms for granted, researchers discovered a third partner in the symbiotic relationship made up by lichens: yeast.

When it comes to lichens, it was believed that they exist as a partnership between an alga or cyanobacteria and a fungus. The scientists discovered a third participant in the mix, yeast, which hid inside the lichen’s cortex.

The study had been conducted by the University of Montana and revealed that the lichens contain basidiomycete which has the purpose of protecting the organisms against predators and microbes.

Even though they tried before, the scientists did not manage to synthesize lichens in the laboratory. The yeasts may also be responsible for the large variety of physical features.

“These yeasts comprise a whole lineage that no one knew existed, and yet they are in a variety of lichens on every continent as a third symbiotic partner. This is an excellent example of how things can be hidden right under our eyes and why it is crucial that we keep studying the microbial world,” said mycologist M. Catherine Aime, leading author of the study.

The first analysis on symbiotic partners was made by the Swiss botanist Simon Schwendener, who explained that some organisms live as a combination of different species that work together. Such was the case with the fungus and the photosynthetic partner. The latter produces food by converting the sun energy and carbon dioxide into sugars. In turn, the fungus offers its partner protection from the environment.

The combination helped lichens to thrive in habitats all over the world, starting from the desert and ending up in the Arctic. They also are the first organisms to live on the ground, which means that the collaboration helped them to evolve.

The yeast may explain why organisms that are genetically identical have distinctive features. For example, Bryoria tortuosa has a yellow color, and it can produce vulpinic acid and Bryoria fremintii is brown and lacks the acid, while both of them are composed of the same fungus and alga.

The researchers believe that it is the yeast that makes the genes express differently.

The study continued with the analysis of 52 genera of lichens, which all proven to have a symbiotic partnership with basidiomycetes.

The organisms had been observed under the microscope for almost two centuries, and yet no one discovered the existence of the yeasts. Even if the microbes have such a long history of science, the researchers still know so little about their role in biological systems.

Image Source: Wikipedia