Mushrooms such as the dermocyboid Cortinarius rubrophyllus are characterized by strikingly colorful fruiting bodies. The molecular dyes responsible for such colors recently experienced a comeback as photoactive compounds with remarkable photophysical and photobiological properties. One of them—7,7′-biphyscion—is a dimeric anthraquinone that showed promising anticancer effects in the low nanomolar range under blue-light irradiation. Compared to acidic anthraquinones, 7,7′-biphyscion was more efficiently taken up by cells and induced apoptosis after photoactivation. However, seasonal collection of mushrooms producing this compound, low extraction yields, and tricky fungal identification hamper further developments to the clinics. To bypass these limitations, we demonstrate here an alternative approach utilizing a precursor of 7,7′-biphyscion, i.e., the pre-anthraquinone flavomannin-6,6′-dimethyl ether, which is abundant in many species of the subgenus Dermocybe. Controlled oxidation of the crude extract significantly increased the yield of 7,7′-biphyscion by 100%, which eased the isolation process. We also present the mycochemical and photobiological characterization of the yet chemically undescribed species, i.e. C. rubrophyllus. In total, eight pigments (1–8) were isolated, including two new glycosylated anthraquinones (1 and 2). Light-dependent generation of singlet oxygen was detected for the first time for emodin-1-O-β-d-glucopyranoside (3) [photophysical measurement: Φ∆ = 0.11 (CD3OD)]. Furthermore, emodin (7) was characterized as promising compound in the photocytotoxicity assay with EC50-values in the low micromolar range under irradiation against cells of the cancer cell lines AGS, A549, and T24. Graphical abstract

Strain QLW-P1FAT50C-4 T , isolated from a shallow acidic freshwater pond located in the Austrian Alps at an altitude of 1300 m, was characterized by investigation of phenotypic, chemotaxonomic and genomic traits. As shown previously, phylogenetic analyses based on 16S rRNA gene sequences place the strain in the cryptic species complex PnecC within the genus Polynucleobacter. The major fatty acids of the strain were C 16:1 ω7c and C 18:1 ω7c. The strain has a genome of 2.23 Mbp with a GC content of 44.9 mol%. The strain encodes a seemingly complete gene cluster for anoxygenic photosynthesis but lacks typical genes for CO 2 assimilation. In order to resolve the phylogenetic position of the strain within the species complex PnecC, concatenated partial sequences of eight housekeeping genes were analysed. The obtained phylogenetic reconstruction did not place strain QLW-P1FAT50C-4 T close to any of the five previously described species within subcluster PnecC. Pairwise average nucleotide identity (ANI) comparisons of whole genome sequences suggested that strain QLW-P1FAT50C-4 T (DSM 24008 T =CIP 111100 T ) represents a novel species for which we propose the name Polynucleobacter wuianus sp. nov.The genus Polynucleobacter and the species Polynucleobacter necessarius were proposed by K. Heckmann and H. J. Schmidt (1987) for bacterial endosymbionts of benthic freshwater ciliates affiliated with the genus Euplotes. Later, it was discovered that free-living strains, closely related to those endosymbiotic strains, represent important planktonic freshwater bacteria (Bahr et al., 1996;Hahn, 2003;Percent et al., 2008;Zwart et al., 2002). The genus Polynucleobacter can be subdivided in at least four subclusters labelled PnecA, PnecB, PnecC, and PnecD (Hahn, 2003). Subcluster PnecC, which includes the endosymbiotic P. necessarius and free-living species, was recognized as being a cryptic species complex, which means that this seemingly very species-rich subcluster cannot be resolved by 16S rRNA gene phylogenies (Hahn et al., 2016a;Hahn et al., 2016b). Taxonomic research on strains affiliated with subcluster PnecC is hampered by the lack of a type strain of the genus

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Strains MWH-EgelM1-30-B4 and MWH-Feld-100 were isolated from the water columns of two freshwater systems. Both strains represent delicate bacteria not easy to work with in laboratory experiments. Phylogenetic analyses of the 16S rRNA genes suggested that both strains were affiliated with the genus Polynucleobacter. Both strains share 16S rRNA gene sequence similarities of >99 % with eight free-living Polynucleobacter type strains, all affiliated with the cryptic species complex PnecC. The full-length 16S rRNA gene sequences of the two strains differ only in two and three positions, respectively, from the sequence of the closest related Polynucleobacter type strain. Genome sequencing of both strains revealed relatively small genome sizes of 2.0 Mbp and G+C contents of 45 mol%. Phylogenetic analyses based on nucleotide sequences of 319 shared protein-encoding genes consistently placed the two strains in taxon PnecC but did not suggest an affiliation with one of the previously described species. Pairwise analyses of whole genome average nucleotide identities (gANI) with representatives of all previously described Polynucleobacter species resulted in both cases throughout in values <80 %. Pairwise comparison of the genomes of the two new strains resulted in gANI values of 83.3 %. All gANI analyses clearly suggested that strains MWH-EgelM1-30-B4 and MWH-Feld-100 represent two novel Polynucleobacter species. We propose for these novel species the names Polynucleobacter hirudinilacicola sp. nov. and Polynucleobacter campilacus sp. nov. and strains MWH-EgelM1-30-B4 (=DSM 23911=LMG 30144) and MWH-Feld-100 (=DSM 24007=LMG 29705) as the type strains, respectively.

The photobiological activity of ten colorful species belonging to subgenus Dermocybe of the basidiomycete genus Cortinarius was investigated. Extracts of all species produced singlet oxygen and are thus photoactive. Pigment analysis was performed and showed similarities of the anthraquinone pigments across the species in dependency to their respective pigmentation types. Detailed content analysis of the pigments in the whole agaricoid fruiting body compared to the three different tissue types (pileus, stipe, and lamellae) revealed that the pigments emodin, dermocybin, and dermorubin, as well as their respective glycosides, are enhanced in the gills. In an independent experiment, the gills were shown to be the most photoactive tissues of the fruiting body. Photobiological experiments with invertebrates (i.e., glassworm Chaoborus crystallinus) proved a phototoxic effect of the methanolic extract of the red blood webcap (Cortinarius sanguineus var. aurantiovaginatus). This work adds further evidence to a common photobiological trait in Cortinarius subgenus Dermocybe and underpins the possibility of a photochemical defense mechanism in fungi. Graphical abstract