Lichens (Xanthoria parietina) - Bio-Indicators for Sulphur and Metallic Elements for Pollution Investigation in Riga City

The aim of the research was to investigate the pollution level of sulphur and metallic elements in Riga city (Freeport of Riga, Kundziņsala, Mežaparks) by using foliose lichens (Xanthoriaparietina) as a bio-indicators. Obtained results show that the Freeport of Riga is the most polluted area comparing with other neatest places in Riga city, Kundziņsala and Mežaparks. Evaluate a washing effect, obtained results shows that lichen thallus contains about 50 % of total amount of sulphur and investigated elements as dust particles on the surface of lichens.

Survival of Xanthoria parietina in simulated space conditions: spectroscopic analysis and vitality assessment

<p>One of the main topics of astrobiology is the study of life limits in stressful environments. This field of research has the aim to understand the physiological and biochemical effects on unprotected biological samples in extreme conditions, such as space. Moreover, these studies provide indications about organisms’ adaptive plasticity under a climate change perspective, the terrestrial geological past and future scenarios, as well as extra-terrestrial habitats as Mars surface.</p> <p>The biological specimen chosen for this study was <em>Xanthoria parietina </em>(L.) Th. Fr. It is a widespread foliose lichen growing on bark and rocks which has a broad spectrum of tolerance to air pollutants such as NO<sub>X</sub> and heavy metals, and resistance to UV-radiation because of the screening properties provided by the secondary metabolism product parietin. In this study we evaluated the ability of this lichen specie to survive under simulated UV space radiation in two different extreme environments i.e., in N<sub>2</sub> atmosphere (N<sub>2</sub>) and in vacuum (10<sup>0</sup>~10<sup>-2</sup> Pa) (VAC).</p> <p>Thalli of <em>X. parietina </em>were randomly collected in a remote area of Tuscany, Italy in June and July 2020. Thalli were dehydrated for 24 h at room temperature (25°C) and stored at -18°C until treatment. Three days before the treatment, thalli were allowed to recover their normal metabolic conditions in a growth chamber at 25 °C and 70 μmol m<sup>-2</sup> s<sup>-1</sup> PAR photons. Overnight, thalli were covered with a black cotton cloth and kept moistened by spraying with distilled water.</p> <p>The simulated UV space radiation was produced using a Xe-enhanced UV lamp with a sun-like emission spectrum (wavelength range 185-2000 nm). The aforementioned atmospheric conditions (N<sub>2</sub> and VAC) were chosen to set up an extreme and dehydrating environment for the lichen. The total absorbed UV radiation dose was 1.34 MJ m<sup>-2</sup> for each exposed sample. During the irradiation, the IR reflectance spectrum of the lichen was monitored <em>in situ</em> with infrared spectroscopy to assess changes in spectral bands.</p> <p>The efficiency of the photosynthetic apparatus was assessed as indicator of vitality, and was expressed in terms of chlorophyll <em>a</em> fluorescence (F<sub>V</sub>/F<sub>M</sub>) and Normalized Difference Vegetation Index (NDVI). The examination of <em>X. parietina</em> recovery through eco-physiological analysis revealed the capacity of this lichen species to survive in extreme conditions such as those simulated in this investigation. It has been highlighted the significant difference between treatments about the photosynthetic efficiency parameters recovery trends, finding that UV-radiation in vacuum produces more intense effects on F<sub>V</sub>/F<sub>M</sub> values. After 72h, UV N<sub>2</sub> fluorescence mean values recovered up to 93% of the starting ones, while UV VAC fluorescence recovered up to 45% of the pre-exposure values. The IR analysis revealed several spectral band changes in the fingerprint region. The most visible variation was the 5200 cm<sup>-1</sup> water band, disappearing in the overtone region. This analysis suggests that the disappearance of H<sub>2</sub>O band after treatment is strictly linked to the thalli dehydration due to the atmospheric simulated conditions represented by N<sub>2</sub> insufflation and high vacuum application. Nevertheless, <em>X. parietina</em> was able to survive to UV-radiation in N<sub>2</sub> atmosphere and in vacuum, and for this reason it may be considered a candidate for further evaluations on its survival capacity in extreme conditions.</p>

Assessment of Lichens as Biomonitors of Heavy Metal Pollution in Selected Mining Area, Slovakia

Lichens have widely been used as bioindicators to reflect the quality of the environment. The present study was conducted to investigate the lichens diversity that grows on the surface of waste heaps from an abandoned old copper mine in Mlynky, Slovakia. In spite of the heavy metalcontaminated environment, we documented twenty species of lichens in the selected site. Taxonomically the most numerous group were represented by Cladonia with seven species, as well other species; namely, Acarospora fuscata, Cetraria islandica, Dermatocarpon miniatum, Hypogymnia physodes, Hypogymnia tubulosa, Lecanora subaurea, Lepraria incana, Physcia aipolia, Porpidia macrocarpa, Pseudevernia furfuracea, Rhizocarpon geographicum and Xanthoria parietina. The content of selected heavy metals (Cu, Fe, and Zn) in the predominant lichens Cetraria islandica, Cladonia digitata, Cladonia pyxidata, Hypogymnia physodes and Pseudevernia furfuracea were analyzed. The highest content of Cu, Fe, and Zn was found in Cladonia pyxidata collected from mine-spoil heaps with concentration 46 ± 4.4, 82.5 ± 22.6, 4.8 ± 1.6 mg/kg, respectively. Interestingly, Cladonia pyxidata collected from the forest surrounding the location showed 15 times lower concentration for Cu. Additionally, similar results were found for Fe and Zn.

Enhanced culturing techniques for the mycobiont isolated from the lichen Xanthoria parietina

Lichens and their isolated symbionts are potentially valuable resources for biotechnological approaches. Especially mycobiont cultures that produce secondary lichen products are receiving increasing attention, but lichen mycobionts are notoriously slow-growing organisms. Sufficient biomass production often represents a limiting factor for scientific and biotechnological investigations, requiring improvement of existing culturing techniques as well as methods for non-invasive assessment of growth. Here, the effects of pH and the supplement of growth media with either D-glucose or three different sugar alcohols that commonly occur in lichens, D-arabitol, D-mannitol and ribitol, on the growth of the axenically cultured mycobiont isolated from the lichen Xanthoria parietina were tested. Either D-glucose or different sugar alcohols were offered to the fungus at different concentrations, and cumulative growth and growth rates were assessed using two-dimensional image analysis over a period of 8 weeks. The mycobiont grew at a pH range from 4.0 to 7.0, whereas no growth was observed at higher pH values. Varying the carbon source in Lilly-Barnett medium (LBM) by replacing 1% D-glucose used in the originally described LBM by either 1%, 2% or 3% of D-mannitol, or 3% of D-glucose increased fungal biomass production by up to 26%, with an exponential growth phase between 2 and 6 weeks after inoculation. In summary, we present protocols for enhanced culture conditions and non-invasive assessment of growth of axenically cultured lichen mycobionts using image analysis, which may be useful for scientific and biotechnological approaches requiring cultured lichen mycobionts.

Ability of metal trace elements accumulation by Lichens, Xanthoria parietina and Ramalina farinacea, in Megres area (Setif, Algeria)

The accumulating ability of the atmospheric Metal Trace Elements (MTE) of two lichenic species thalli; Xanthoria parietina and Ramalina farinacea were evaluated in the region of Megres. The recorded concentrations of MTE (Fe, Cu, Mn, Cd, and Pb) were determined by atomic absorption spectrophotometry (AASF). The ability to accumulate MTE in X. parietina thalli is considerably greater than that of the fruticulous lichen R. farinacea in all stations studied. The general pattern of the elements accumulated in the thalli of the two species in decreasing order of their concentrations was Fe> Mn> Pb> Cu> Cd. The Fe values are very high in X. parietina thalli with an average of 35237.5 ± 3394.2 mg/kg dry wt. In contrast, the Pb concentrations are high, especially in the southern station of the Megres region. The results showed that X. parietina is a hyper-accumulating species of MTE, compared to R. farinacea. This work highlights the ecological importance of this species as a stable and resistant pioneer in this fragile region.

PHOTOPROTECTIVE, CYTOTOXIC AND PHOTOMODIFYING ACTIVITY OF LICHEN BIOMASS NON-POLAR FRACTIONS AGAINST HUMAN KERATINOCYTE (HaCAT)

In vitro, the photoprotective, cytotoxic and photomodifying properties of hexane and benzene extracts from the widely distributed in Belarus lichens Cladonia arbuscula, Evernia prunastri, Hypogymnia physodes, Ramalina pollinaria and Xanthoria parietina in the culture of human keratinocytes (HaCAT), are estimated. It was found that these extracts are not photoprotective, they have a photomodifying effect upon irradiation of keratinocyte cultures with ultraviolet light. Hexane extract of E. prunastri and benzene extracts of R. pollinaria and H. physodes at a concentration of 2.5 μg/ml are photoprotectors that weaken the effect of ultraviolet radiation by 1.6 ÷ 1.8 times. Extracts of C. arbuscula and X. parietina are photosensitizers – they increase the toxic effect of ultraviolet radiation by 10 or more times, regardless of the concentration of the extract in the nutrient medium. Hexane and benzene extracts of C. arbuscula and H. physodes lichens are cytotoxic to the HaCAT culture. With an increase in the dose of ultraviolet irradiation of keratinocytes from zero to lethal values, the benzene extract of R. pollinaria acted as a photoprotector at a concentration of 2.5 μg / ml, and as a photosensitizer at higher concentrations. The hexane and benzene extracts of E. prunastri and H. physodes exhibited sensitizing properties that increased with an increase in the concentration of lichen extracts. C. arbuscula hexane extract and X. parietina benzene extract were the most potent photosensitizers.

Molecular phylogenetic analyses reveal two new synonyms of Xanthoria parietina

Molecular analyses of the recently described Xanthoria polessica collected from the type locality and of the Australian species X. coomae were used to determine whether these taxa are distinct species or fall within the wide phenotypic variation of the well-known and cosmopolitan X. parietina. Our results clearly indicate that both taxa should be considered as synonyms of X. parietina since the infraspecific morphological range is accommodated by the observed variation in the thallus and lobe size, their color, position of apothecia, the shape of ascospores, and width of ascospore septum.