Mycobiomes of Six Lichen Species from the Russian Subarctic: A Culture-Independent Analysis and Cultivation Study

Lichens are defined as holobionts, whose thalli are known to contain a significant diversity of bacteria, fungi, protozoa, and viruses. Research into the presence of these organisms in lichens remains limited. Therefore, assessing the diversity of fungi in different species of lichen remains a relevant task. In this study, we analysed the taxonomic composition of the mycobiome of six lichen species from northern Russia. To achieve this, we employed high-throughput sequencing and cultivation methods using a modified nutrient medium. The study obtained data on the dominance of fungi from the classes Dothideomycetes, Eutypomycetes, Leotiomycetes and Tremellomycetes in the lichen samples studied. We found that the most common taxa among the lichen species studied were lichenicolous or parasitic fungi belonging to the genera Athelia, Epithamnolia and Cladosporium. The diversity of OTUs in Nephromopsis nivalis thalli that were processed using an abrasive to remove epiphytic fungi was found to be 30-50% lower than in intact thalli. Our findings suggest that the characteristics of the lichen species and its environment within the biocenosis can influence the diversity and abundance of fungi in thalli. Ninety-two fungal cultures were obtained and identified at various phylogenetic levels. Six strains were identified that presumably belong to new families within the orders Lecanorales, Tremellales, Septobasidiales and Myriangiales. We discovered that modifying cultivation methods can hasten the quest for novel, hitherto unexplored strains of lichenophilic fungi.