Leho Tedersoo

Phylogenetic taxonomy and classification of fungi

More than 160,000 species of fungi have been described worldwide. It is estimated that there are two to three million species in the fungal kingdom, many of them invisible to the naked eye. The majority of these live in the soil, playing crucial roles in ecosystem functioning, such as decomposing organic matter and supporting plants with nutrient uptake. How can these microorganisms, often only identified through their DNA, be described and communicated?

Over the past 15 years, Tedersoo’s research group has collected tens of thousands of soil and leaf samples, as well as water and household dust samples, whose DNA sequences often indicated the presence of species and phylogenetic lineages not yet described. The project aims to systematise and describe members of the 95% majority of previously unclassified microscopic fungi, and other eukaryotic organisms not yet included in the current tree of life. A new system for DNA-based classification of organisms will then be developed.

Result

The current methods for describing and communicating fungal species have proven insufficient. As a result, many are not covered in the tree of life depicting the evolution and taxonomic relationships of living species. What has not been described is hard to protect or, in the case of pathogens, to prevent systematically.

Tedersoo and his team plan to apply the latest methods of molecular biology and genomics, which make it possible to obtain information necessary for species identification even from a single cell. This is particularly useful in environmental monitoring, where environmental DNA samples are increasingly used to provide insights into, for example, the species living in a body of water based on the genetic material present in water samples. Tedersoo’s group partners with the European Molecular Biology Laboratory (EMBL) in Germany where novel methods are used and members of the research group are trained to build relevant laboratory capabilities in Tartu for future collaboration.

Impact

The applications are almost exclusively related to further research, as they make it possible to recognise these undescribed organisms in subsequent studies. Theoretically, these organisms may also offer some biotechnological potential because of the unique enzymes they contain.

The researchers led by Tedersoo are developing principles for a new taxonomic system, tackling questions such as how to include the existing taxonomic data in the new system to avoid the emergence of two parallel approaches to species description. Although the project is very time-consuming, Tedersoo is hopeful that within the next ten years, it will be possible to describe representatives of very large and widespread groups of microscopic fungi at the phylum, order, or family level, which would help establish the basic structure of the fungal evolutionary tree. The project brings special attention to Estonia, because many new taxa are named according to the localities in Estonia where they were found.