Compendium of the most significant studies with reference to properties, intake, effects.

Paoli L, Fačkovcová Z, Guttová A, Maccelli C, Kresáňová K, Loppi S. Evernia Goes to School: Bioaccumulation of Heavy Metals and Photosynthetic Performance in Lichen Transplants Exposed Indoors and Outdoors in Public and Private Environments. Plants (Basel). 2019 May 13;8(5):125. doi: 10.3390/plants8050125. 

Abstract. Recently indoor air quality (IAQ) has become a key issue, especially in schools, where children spend most of the day. Only in a few cases IAQ was investigated using lichens as biomonitors. During autumn 2017, lichens (Evernia prunastri) were exposed for two months indoors and outdoors in public (schools) and private (dwellings) environments, in both rural and urban areas of Slovakia. The bioaccumulation of selected elements and the physiological status of the samples were considered. The content of heavy metals increased in samples exposed outdoors for 11 out of 12 elements (Al, As, Cd, Cr, Cu, Fe, Pb, S, Sb, V and Zn, but not Ca) in the urban area and for 5 (As, Cd, Cu, Pb and Sb) in the rural area. Indoor concentrations were overall similar, both in rural and urban buildings, independently of the outdoor conditions. An indoor accumulation occurred only for Cd, Cu and Pb. An indoor origin was suggested for Cd, while for Cu and Pb, outdoor penetration (car traffic) is the likely cause of indoor values. Indoor exposed lichens maintained their vitality (as reflected by chlorophyll a fluorescence emission). This latter result further supports the use of lichen biomonitoring as a suitable method for assessing IAQ.

Calchera A, Dal Grande F, Bode HB, Schmitt I. Biosynthetic Gene Content of the 'Perfume Lichens' Evernia prunastri and Pseudevernia furfuracea. Molecules. 2019 Jan 8;24(1):203. doi: 10.3390/molecules24010203.

Abstract. Lichen-forming fungi produce a vast number of unique natural products with a wide variety of biological activities and human uses. Although lichens have remarkable potential in natural product research and industry, the molecular mechanisms underlying the biosynthesis of lichen metabolites are poorly understood. Here we use genome mining and comparative genomics to assess biosynthetic gene clusters and their putative regulators in the genomes of two lichen-forming fungi, which have substantial commercial value in the perfume industry, Evernia prunastri and Pseudevernia furfuracea. We report a total of 80 biosynthetic gene clusters (polyketide synthases (PKS), non-ribosomal peptide synthetases and terpene synthases) in E. prunastri and 51 in P. furfuracea. We present an in-depth comparison of 11 clusters, which show high homology between the two species. A ketosynthase (KS) phylogeny shows that biosynthetic gene clusters from E. prunastri and P. furfuracea are widespread across the Fungi. The phylogeny includes 15 genomes of lichenized fungi and all fungal PKSs with known functions from the MIBiG database. Phylogenetically closely related KS domains predict not only similar PKS architecture but also similar cluster architecture. Our study highlights the untapped biosynthetic richness of lichen-forming fungi, provides new insights into lichen biosynthetic pathways and facilitates heterologous expression of lichen biosynthetic gene clusters.

Munzi S, Cruz C, Maia R, Máguas C, Perestrello-Ramos MM, Branquinho C. Intra- and inter-specific variations in chitin in lichens along a N-deposition gradient. Environ Sci Pollut Res Int. 2017 Dec;24(36):28065-28071. doi: 10.1007/s11356-017-0378-3.

Abstract. The mechanisms of nitrogen (N) tolerance in lichens are not yet fully understood. Here, we investigated how the increase of chitin content is related with N excess at inter- and intra-specific levels, by using species with differing ecological N tolerances (the tolerant Xanthoria parietina and Parmotrema hypoleucinum and the sensitive Evernia prunastri and Usnea sp.) and thalli of X. parietina and P. hypoleucinum from sites with different availabilities of N of agricultural origin (livestock), as confirmed by lichen N content and δ¹⁵N. Nitrogen, chitin (N-containing compound), and ergosterol contents were measured in lichen thalli. Nitrogen and chitin contents were higher in tolerant species than those in sensitive ones (inter-specific level) and in thalli collected from the N-polluted site than in thalli from the clean site (intra-specific level). We suggest that chitin contributes to N stress tolerance in lichens, and that excess N can be partially stored as chitin (non-toxic form) in the cell walls of tolerant species.

Safety

Nardelli A, Drieghe J, Claes L, Boey L, Goossens A. Fragrance allergens in 'specific' cosmetic products. Contact Dermatitis. 2011 Apr;64(4):212-9. doi: 10.1111/j.1600-0536.2011.01877.x. 

Abstract.  Background: Together with preservative agents, fragrance components are the most important sensitizing culprits in cosmetic products. Objectives: To identify the nature of the fragrance ingredients responsible for allergic contact dermatitis (ACD) from specific cosmetic products. Methods: Between 2000 and 2009, positive patch test reactions or positive usage tests with the patients' own cosmetic products, were recorded using a standardised form. Results: Of the 806 cosmetic records, corresponding to 485 patient files, 344 concerned reactions to fragrance ingredients that according to the label were present ('Presence Confirmed' [PC n = 301]) or suspected to be present ('Presence Not Confirmed' [PNC n = 376]) in the causal cosmetic products used, which belonged to 15 different categories, toilet waters/fine perfumes being the most frequent. Geraniol in fragrance mix I (FM I) and hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC) in FM II were the most frequent PC, and together with hydroxycitronellal and Evernia prunastri (oak moss) the most frequent PNC ingredients in the causal cosmetic products. Limonene was the most frequent PC confirmed fragrance allergen. Conclusions: This study not only underlines the usefulness of fragrance-ingredient labelling in order to identify the causal allergen(s) present in specific cosmetic products, but may also provide information on trends in the actual use of sensitizing fragrance ingredients in them.

Vannini A, Jamal MB, Gramigni M, Fedeli R, Ancora S, Monaci F, Loppi S. Accumulation and Release of Mercury in the Lichen Evernia prunastri (L.) Ach. Biology (Basel). 2021 Nov 18;10(11):1198. doi: 10.3390/biology10111198.

Abstract. This study investigated the dynamics of the accumulation and release of Hg2+ in lichens, using Evernia prunastri (L.) Ach. as a model species. Thalli were incubated with solutions containing 1, 10, and 100 µM Hg2+ and then exposed for 1, 2, 3, 6, 12, 18, and 24 months at the Botanical Garden of the University of Siena (a location free from local Hg sources). Lichen samples accumulated Hg proportionally to the exposure concentration, and after the exposure, reductions over time were evident, already starting from 1-2 months. After 24 months, samples released 72-74 (healthy thalli) to 94% (unhealthy thalli) of the accumulated Hg, but control values of untreated samples were never reached. Depending on the Hg content after the exposure, stable decreased concentrations were reached after 6-24 months. The results of this study highlight the ability of the lichen E. prunastri to reflect rapidly increasing environmental Hg concentrations, as well as to indicate an ameliorated situation (e.g., the closure of an Hg source). However, we have found evidence that an acute pollution episode can influence the content of Hg in lichens for several years.