Fungi involved in lichen symbioses produce a large array of secondary metabolites that are often diagnostic in the taxonomic delimitation of lichens. The most common lichen secondary metabolites—polyketides—are synthesized by polyketide synthases, particularly by Type I PKS (TI-PKS). Here, we present a comparative genomic analysis of the TI-PKS gene content of 23 lichen-forming fungal genomes from Ascomycota, including the de novo sequenced genome of Bacidia rubella. Firstly, we identify a putative atranorin cluster in B. rubella. Secondly, we provide an overview of TI-PKS gene diversity in lichen-forming fungi, and the most comprehensive Type I PKS phylogeny of lichen-forming fungi to date, including 624 sequences. We reveal a high number of biosynthetic gene clusters and examine their domain composition in the context of previously characterized genes, confirming that PKS genes outnumber known secondary substances. Moreover, two novel groups of reducing PKSs were identified. Although many PKSs remain without functional assignments, our findings highlight that genes from lichen-forming fungi represent an untapped source of novel polyketide compounds.

Lichens have developed numerous adaptations to optimise their survival under harsh abiotic stress, colonise different substrates, and reach substantial population sizes and high coverage in ice-free Antarctic areas, benefiting from a symbiotic lifestyle. As lichen thalli represent consortia with an unknown number of participants, it is important to know about the accessory organisms and their relationships with various environmental conditions. To this end, we analysed lichen-associated communities from Himantormia lugubris, Placopsis antarctica, P. contortuplicata, and Ramalina terebrata, collected from soils with differing deglaciation times, using a metabarcoding approach. In general, many more Ascomycete taxa are associated with the investigated lichens compared to Basidiomycota. Given our sampling, a consistently higher number of lichen-associated eukaryotes are estimated to be present in areas with deglaciation times of longer than 5000 years compared to more recently deglaciated areas. Thus far, members of Dothideomycetes, Leotiomycetes, and Arthoniomycetes have been restricted to the Placopsis specimens from areas with deglaciation times longer than 5000 years. Striking differences between the associated organisms of R. terebrata and H. lugubris have also been discovered. Thus, a species-specific basidiomycete, Tremella, was revealed for R. terebrata, as was a member of Capnodiales for H. lugubris. Our study provides further understanding of the complex terricolous lichen-associated mycobiome using the metabarcoding approach. It also illustrates the necessity to extend our knowledge of complex lichen symbiosis and further improve the coverage of microbial eukaryotes in DNA barcode libraries, including more extended sampling.

The molecular phylogeny of Bacidia s.s. in the Russian Far East was investigated using 62 nucleotide sequences from the ITS nrDNA region, 22 of which were newly obtained. Phylogenetic reconstructions employed Bayesian inference and maximum likelihood searches using MrBayes and RAxML. In addition, ITS2 secondary structures added further support using Compensatory Base Changes. As a result of morphological and phylogenetic studies, four new species of Bacidia are described. Bacidia areolata sp. nov. belongs to the suffusa group. It was collected once in Khabarovskiy Krai, the Russian Far East, on the bark of Acer tegmentosum and is closely related to B. suffusa but differs in having a smooth, cracked to areolate thallus and shorter spores. Bacidia elongata sp. nov. is a member of the fraxinea group and is similar to B. fraxinea but differs in having a wide zone of cells with enlarged lumina along the edge of the exciple. In fact, this zone of enlarged cells, in combination with its overall habit, places it morphologically close to B. suffusa, B. millegrana and B. campalea. Bacidia kurilensis sp. nov. is a basal member of the laurocerasi group and closely related to B. biatorina, B. heterochroa, B. laurocerasi and B. salazarensis. However, the combination of a granular thallus, large black apothecia and a green hue in the upper part of the exciple edge as well as in the epihymenium sets it apart from the species mentioned above. Bacidia sachalinensis sp. nov. resolves as a strongly supported member of the polychroa group and is known from a single locality in Sakhalin, the Russian Far East. Its thallus structure and apothecium colour are variable, which is typical for the polychroa group, but it differs from B. polychroa by having shorter spores with fewer septa and a mainly smooth to areolate thallus.

Muchnik, E. E, Tsurykau, A., Otte, V., Breuss, O., Gerasimova, J. V. & Cherepenina, D. A. 2022. Neue und andere bemerkenswerte Funde lichenisierter und lichenicoler Pilze aus dem zentralen europäischen Teil Russlands II. – Herzogia 35: 494 –509. Funde von fünfzehn Arten lichenisierter und zehn lichenicoler Pilzen werden aufgeführt. Lecanora substerilis, Rufoplaca subpallida, Sarcogyne praetermissa und Verrucaria fuscoatroides werden erstmals für Russland nachgewiesen. Didymocyrtis epiphyscia s. lat., Epithamnolia longicladoniae, Lecanora barkmaniana und Sclerococcum epicladonia sind neu für den europäischen Teil Russlands. Arthonia phaeophysciae, Bacidina mendax, Cladonia novochlorophaea, Gyalecta carneola, Lichenoconium aeruginosum und Verrucaria pilosoides sind neu für den mittleren Teil des europäischen Russlands. Weitere neun Arten (Cliostomum corrugatum, Gyalecta derivata, Lichenoconium lecanorae, Micarea soralifera, Physciella chloantha, Taeniolella phaeophysciae, Talpapellis beschiana, Telogalla olivieri, Verrucaria ochrostoma) wurden bisher äußerst selten beobachtet. Auf ihre kennzeichnenden Merkmale und ihre Verbreitung wird kurz eingegangen.