Lichens as biodeterioration agents and biomonitors

Summary The role played by lichens in archaeological and monumental areas as biodeteriogenic agents is discussed. Methods now used in the qualitative and quantitative analysis of lichenic colonisation on stonework are considered, and their standardisation is proposed. Lichens not only play a role in degradation but are also used as indicators of environmental characteristics. Thus the function of lichens as biomonitors in the broadest sense is discussed. The authors propose a methodological record with different approaches (auto ecology, synecology, phytosociology) that could be applied to stonework, historical and archaeological areas with the aid of integrated methodologies (biological traps, lichenometry, biomonitoring).     

Immunological aspects of a space flight to Mars

The effects on the immune system of a 520-day isolation in a confined environment, simulating some conditions of a manned space flight to Mars, have been studied. A set of signs of adaptational reorganization, including quantitative and functional changes in innate and adaptive immunity, have been recorded. The most significant ones include the changes in the system of Toll-like receptors (TLRs) manifested as a decrease in the content of circulating monocytes and granulocytes expressing TLR2, TLR4, and TLR6; a decrease in the functional capacity of cellular factors of natural cytotoxicity or natural killer cells (NK cells); an increased ability of T cells and B cells to express on their surface the CD69 early activation marker; and an increase in phytohaemagglutinin (PHA)-induced secretion by cytokines in peripheral blood mononuclear cells. Intense mobilization of adaptive immunity and qualitative changes of its functions demonstrates the adaptive adjustment of the body in response to the combined effect of unfavorable factors to preserve immune homeostasis.     

Lichens as biomarkers for dew amount and duration in the Negev Desert

We studied the lichen diversity on cobbles at 18 stations located within 4 aspects of a second order drainage basin near Sede Boqer at the Negev Highlands, Israel, where dew was found to be the main water source for lichens. At each station 10 cobbles were randomly chosen and the lichen community composition and structure were investigated and compared to the dew amount and duration that characterize each station. Excluding the wadi stations that showed a very heterogeneous population (probably originating from cobbles that rolled down from both adjacent slopes) and were therefore excluded from the analysis, all other stations were grouped into 5 clusters that showed a close link with the dew moisture regime. Lichen distribution pointed to species which can serve as biomarkers for dew amount and especially for dew duration. The data imply that at a meso-scale, lichens can provide information regarding the dew regime of habitats where no microclimatological data are available.     

Lichens as rapid bioindicators of pollution and habitat disturbances in the tropics

Lichens have value as bioindicators of environmental pollution, climate change, and ecological continuity. Extensive work has been undertaken in temperate areas, but in only few cases have the techniques been applied in the tropics. Most tropical studies to date are in relation to air pollution and forest disturbance, but these are scattered geographically and remain to be undertaken in most tropical regions. The potential of lichens as rapid bioindicators in the tropics can start to be realized even where the species described are not fully identified as they are perennial and separable by eye or hand lens, and a lack of training is identified as the main constraint. An extensive bibliography is included.     

Lichens on ancient mortars

The study of three archaeological sites of southern Spain showed that mortar is a building material easily colonized by a diversity of calcicolous and rather nitrophilous lichens. The interface between lichen and mortar showed an intense chemical activity of the hyphae producing extensive alteration on the surface. The nature and amount of the mortar components greatly influenced the colonizing species and the patterns of alteration.     

新疆地衣研究概述

根据1985年以来的研究资料并结合前人的研究报道,综述了新疆地衣在分类学、地理区系、生态学和应用等方面的研究历史和现状。重点分析了新疆地衣的地理成分、分布型和不同环境、基物条件下的地衣种群及群落,文中还阐述了新疆地衣研究的未来发展趋势,并进行了展望。为新疆地衣物种多样性的有效保护、地衣资源的合理开发利用等方面提供了重要的理论依据。     

Ice Nucleation Activity in Lichens

A newly discovered form of biological ice nucleus associated with lichens is described. Ice nucleation spectra of a variety of lichens from the southwestern United States were measured by the drop-freezing method. Several epilithic lichen samples of the genera Rhizoplaca, Xanthoparmelia, and Xanthoria had nuclei active at temperatures as warm as −2.3°C and had densities of 2.3 × 10⁶ to more than 1 × 10⁸ nuclei g⁻¹ at −5°C (2 to 4 orders of magnitude higher than any plants infected with ice nucleation-active bacteria). Most lichens tested had nucleation activity above −8°C. Lichen substrates (rocks, plants, and soil) showed negligible activity above −8°C. Ice nucleation-active bacteria were not isolated from the lichens, and activity was not destroyed by heat (70°C) or sonication, indicating that lichen-associated ice nuclei are nonbacterial in origin and differ chemically from previously described biological ice nuclei. An axenic culture of the lichen fungus Rhizoplaca chrysoleuca showed detectable ice nucleation activity at −1.9°C and an ice nucleation density of 4.5 × 10⁶ nuclei g⁻¹ at −5°C. It is hypothesized that these lichens, which are both frost tolerant and dependent on atmospheric moisture, derive benefit in the form of increased moisture deposition as a result of ice nucleation.     

The Effect of Desiccation on Cation Location in Lichens

Experiments were performed on 15 lichen species from a rangeof different habitats, to compare the cellular location of cationsin desiccation stressed and unstressed material. It was shownthat desiccation caused a significant loss of intracellularpotassium and magnesium in some species and that the loss canbe related to the water availability in the natural habitat.During leakage some immobilization of cations occurs on to thecell wall cation exchange sites. The proportion immobilizeddepends on the nature of the cation released and the natureof the cations already present on the exchange sites. Desiccation-stressedlichens can partially or wholly recover their original cationdistribution by incubation in a humid environment. Desiccation resistance and recovery indices are proposed forlichens. These allow comparisons to be made with bryophytesand conclusions to be drawn about their respective micro-environments. lichens, bryophytes, cation distribution, desiccation stress     

Of Lichens,Caribou and Tuna

Delayed skeletal maturation has been long accepted as a correlate of mental retardation. Three hundred mentally retarded children were examined for skeletal age and failed to show any overall delay of bone age as compared to chronological age. Further, birth weight was found to be unrelated to bone age maturity. Children with severe levels of retardation displayed significant delay in bone development only when profound physical disability was also present. In eight diagnostic categories of mental retardation, only those with metabolic syndromes showed any significant delay in skeletal system maturation. Conversely, mongoloid children showed a larger-than-chance percentage of advanced bone maturation. Skeletal measures therefore are perhaps more reflective of etiological states than of diagnostic classifications in mental retardation.     

地衣次生代谢产物及其生物活性研究进展

地衣是一类独特的生物有机体,其体内合成了多种特殊的次生代谢产物,主要为缩酚酸、缩酚酸环醚、缩酚酮、二苯并呋喃等类化合物。这些次生代谢产物具有多样的生物活性,包括抗氧化、抗辐射、抗菌、抗病毒、抗肿瘤、植物生长抑制和昆虫拒食等活性。本文对近40年来有关地衣化学及生物活性方面的研究进行综述,为地衣资源的进一步研究和开发提供参考。     

Life on Mars

Abstract

There is evidence that at one time Mars had liquid water habitats on its surface. Studies of microbial communities in cold and dry environments on the Earth provide a basis for discussion of the possible nature of any life that may have existed on Mars during that time. Of particular relevance are the cyanobacterial communities found in hypolithic and endolithic habitats in deserts. Microbial mats found under ice-covered lakes provide an additional possible Martian system. Results obtained from these field studies can be used to guide the search for fossil evidence of life on Mars. It is possible that in the future life will be reintroduced on Mars in an effort to restore that planet to habitable conditions. In this case the organisms under study as exemplars of past life may provide the hardy stock of pioneering Martian organisms. These first organisms must be followed by plants. The feasibility of reviving Mars will depend on the ability of plants to grow in an abundance of CO₂ but at extremely low pressures, temperatures, O₂, and N₂ levels. On Mars, biology was, and is, destiny.     

Lichens as bioindicators of temporal variations in air quality around Thessaloniki, northern Greece

The epiphytic lichen vegetation of 20 sites around Thessaloniki (Macedonia, northern Greece) surveyed in 1987 was sampled again in 1997 to monitor any changes in lichen communities and consequently in air quality. A general impoverishment in lichen communities was recorded in the 10-year period, presumably chiefly due to changes in the air pollution status. A small increase in lichen species diversity was recorded in some stations, probably as a result of the buffering capacity of airborne dust.     

Microhabitats and Chemical Microenvironments under Saxicolous Lichens Growing on Granite

Lasallia hispanica, Parmelia omphalodes, and Cornicularia normoerica, saxicolous thalli growing on granite, show a close relationship with other lichens and microorganisms living in the lithic substrate beneath them. The lithobiontic community is an accumulation of microorganisms at an interface forming a biofilm, which interacts with the lithic substrate both geophysically and geochemically. Because of their fruticose and foliose morphology, the saxicolous species examined here are mainly involved in geophysical processes, but in the proximity of their attachment structures, geochemical processes may also be observed. On the other hand, fungi, algae and cyanobacteria forming crustose lichens, as well as free-living lithobiontic microorganisms, are known to show combined geophysical and geochemical action, mainly on laminar minerals. The substrate zone where the saxicolous lichens are attached is most affected by weathering reactions and shows the highest co-occurrence of lithobiontic microorganisms. The physical and chemical properties of the substrate, along with lichen and microorganism activity, determine different microenvironments and microhabitats. The ecological functioning of these lithobiontic communities is not yet fully understood, and research efforts similar to the present are needed to confirm that their development is influenced by interrelations between different community members and the substrate, as suggested here.     

Metal Determination by EDXRF in Lichens

Biological Trace Element Research - Samples ofEvernia prunastri, collected in a mountainous zone, were exposed in urban and highly industrialized areas in order to monitor the atmospheric...     

Lichens as a potential natural source of bioactive compounds: a review

Biological activity of material whether known in folk medicine or observed in planned screening program has been the starting point in the drug research. The general pattern is the isolation of active principles, elucidation their structures, followed by attempts for modulation of its activity potential by chemical modification. Lichens are valuable plant resources and are used as medicine, food, fodder, perfume, spice, dyes and for miscellaneous purposes throughout the world. Lichens are well known for the diversity of secondary metabolites that they produce. Compounds isolated from various lichen species have been reported to display diverse biological activities. Here we review the medicinal efficacy of lichen substances, which intends to explore the pharmaceutical potential of lichen substances.     

Lichens on branches of Siberian fir (Abies sibirica Ledeb.) as indicators of atmospheric pollution in forests

The abundance distribution of different ecological groups of lichens depending on bark pH has been studied on 1- to 24-year shoots of Siberian fir in the mountains of southern Siberia. Along with acidophytic lichens commonly found on the Siberian fir (Usnea sp., Bryoria sp., etc.), its young shoots are also colonized by nitrophytic species (Physcia tenella, Melanelia exasperatula, etc.), which is evidence for the increasing pH of shoot bark. The proportion of thalli of nitrophytic lichen species shows a significant positive correlation with the pH of the upper (dusted) bark layer and is greater in the Eastern Sayan (at bark pH averaging 5.4) than in the Western Sayan (pH 4.7). The trends revealed in this study may be used for indication of pollution and ecological monitoring of forest ecosystems.     

沂山地衣研究

对采自山东省沂山的370余个地衣标本进行分类整理,共鉴定出12个科26个属59个种(包括2个变种)。其中山东省新记录属5个,新记录种35个。