Response of calcareous grassland vegetation to mowing and fluctuating weather conditions

Question: What determines the balance between the cover values of vascular plants, lichens and mosses in dry calcareous grassland communities? Location: Western Estonia. Methods: A five‐year (2001–2005) study was conducted in a dry calcareous grassland. The cover of mosses, lichens and vascular plants and all moss species was recorded in permanent plots. Vascular plants were cut in half of the plots. Data from a nearby weather station were used to calculate mean values of different weather parameters and a summer moisture index for the study years. Results: Significant differences in cover values between years were found. The fluctuations of total moss cover and the cover of the dominating moss species Ctenidium molluscum followed changes in annual precipitation. Both cover values were highest in years with high precipitation. The cover change of vascular plants was best characterized by the moisture index of the growth period (three summer months). Summers with high moisture indexes facilitated vascular plant and lichen growth. Annual precipitation and the cover of mosses had a negative influence on the cover of vascular plants. The cutting of vascular plants did not have a significant effect on moss and lichen cover. Conclusions: 1. On dry calcareous grasslands the growth of mosses is enhanced by high annual precipitation, while the growth of vascular plants and lichens is influenced rather by the high summer moisture index. The cover of vascular plants is inhibited by the large moss cover. 2. Mowing of vascular plants does not influence the cover of mosses and lichens.     

Environmental context shapes the bacterial community structure associated to Peltigera cyanolichens growing in Tierra del Fuego,Chile

The structure of the associated bacterial community of bipartite cyanolichens of the genus Peltigera from three different environmental contexts in the Karukinka Natural Park, Tierra del Fuego, Chile, was assessed. The sampling sites represent different habitat contexts: mature native forest, young native forest and grassland. Recently it has been determined that the bacterial community associated to lichens could be highly structured according to the mycobiont or photobiont identities, to the environmental context and/or to the geographic scale. However, there are some inconsistencies in defining which of these factors would be the most significant on determining the structure of the microbial communities associated with lichens, mainly because most studies compare the bacterial communities between different lichen species and/or with different photobiont types (algae vs. cyanobacteria). In this work bipartite lichens belonging to the same genus (Peltigera) symbiotically associated with cyanobacteria (Nostoc) were analyzed by TRFLP to determine the structure of the bacterial community intimately associated with the lichen thalli and the one present in the substrate where they grow. The results indicate that the bacterial community intimately associated differs from the one of the substrate, being the former more influenced by the environmental context where the lichen grows.     

Yeast population of the Kindo Peninsula lichens

Yeast abundance and species diversity in the lichens collected at the Kindo Peninsula (Karelia) were studied. A total of 14 lichen species analyzed belonged to the genera Bryoria, Cladonia, Hypogymnia, Icmadophila, Nephroma, Peltigera, and Ramalina. Abundance of cultured yeasts in lichens was intermediate between soil and phyllosphere. The average yeast number on lichens was ~2.5 × 10³ CFU/g, while it exceeded 8 × 10³ CFU/g on plants and reached only 1 × 10³ CFU/g in soil. Yeast population of different parts of Cladonia lichens was found to vary significantly in abundance, species diversity, and community structure. The highest yeast abundance and diversity were revealed in the growth zone. Fifteen yeast species were isolated from lichens, including 6 basidiomycetous and 9 ascomycetous ones. Unlike soils and plants, yeast population of lichens consisted mainly of ascomycetous species, with predominance of Candida sphagnicola and anamorphous yeasts of the genus Dothiora. These results show that yeasts from different taxonomic and ecological groups are a necessary component of lichens; conditions favoring the preservation and development of specific yeast communities differing from the typical soil and phyllosphere yeast complexes are formed in the lichens of northern taiga forests.     

Vegetation of Barton Peninsula in the neighbourhood of King Sejong Station (King George Island,maritime Antarctic)

Plant communities were studied on Barton Peninsula around King Sejong Station on King George Island, maritime Antarctic. The objective of this study was to document the occurrence and distribution of plant assemblages to provide the bases for monitoring the effects of environmental changes and human impact on the vegetation of this area. Approximately 47% of the investigated area was covered by vegetation. Crustose lichens showed the highest mean cover (21%) among vegetation components. The total mean cover of the four dominant taxa, together with the other three major subdominant components, i.e., Usnea spp., Andreaea spp. and Sanionia georgico-uncinata, was 78.2% of the total cover of all the species. Lichen cover and species diversity increased with altitude and the time of exposure from snow. Lichens contributed substantially more to the increased species density and diversity than did bryophytes. Ten plant communities were recognized within the study area. All of them belong to the Antarctic cryptogam tundra formation; they were grouped into four subformations: fruticose lichen and moss cushion subformation, crustose lichen subformation, moss carpet subformation and moss hummock subformation. The moss turf subformation was not found on this region. The Antarctic herb tundra formation was also not found; however, the populations of both Antarctic vascular plants have rapidly expanded around Barton Peninsula in recent years, which may allow development of the Antarctic herb tundra formation in the future.     

Environmental factors and ground disturbance affecting the composition of species and functional traits of ground layer lichens on grey dunes and dune heaths of Estonia

A unique, species‐rich and endangered lichen biota can be found on European coastal and inland sand dunes. However, it is increasingly affected by natural succession as well as by anthropogenic disturbances. We studied lichen diversity on the grey dunes and dune heaths of coastal and inland regions of Estonia. A total of 28 study plots were investigated; in each 0.1 ha study plot general environmental variables and anthropogenic disturbances were described and all epigeic lichen species were identified. We found 66 lichenized fungus (lichen) species, including several rare and ten red‐listed lichens. Multivariate analysis (DCA, CCA) was performed to examine gradients in species composition and to relate variation in species data to environmental factors. In addition, we used redundancy analysis (RDA) to relate variation in species’ trait composition to environmental factors. Species composition on grey dunes differed significantly from that on dune heaths. The characteristic species for grey dunes are, besides several Cladonia species, foliose lichens, e.g. Hypogymnia physodes, Parmelia sulcata and Peltigera spp. Also species’ traits composition was different for either habitat, indicating that sorediate lichens, foliose lichens, lichens with cyanobacterium as the main photobiont, and sparsely branched Cladonia species dominate on grey dunes, while esorediate, green‐algal, crustose and richly branched fruticose lichens are common on dune heaths. Soil pH was the most essential environmental variable for determining both species composition and species’ traits composition. The composition of lichen species was also significantly influenced by forest closeness, soil Mg content and cover of bare sand; the effect of ground disturbances was low compared to the effect of these environmental factors. To protect and conserve the species‐rich lichen biota, it is necessary to protect the dune habitats from building activity, to avoid overtrampling in recreation areas and to regularly remove shrubs and trees.     

Carotenoid composition and metabolism in green and blue-green algal lichens in the field

The carotenoid composition of 33 species of green algal lichens and 5 species of blue-green algal lichens was examined and compared with that of the leaves of higher plants. As in higher plants, green algal lichen species which were found in both shade and full sunlight exhibited higher levels of the carotenoids involved in photoprotective thermal energy dissipation (zeaxanthin as well as the total xanthophyll cycle pool) in the sun than in the shade. This was particularly true when thalli were moist during exposure to high light, or presumably became desiccated in full sunlight. However, the reverse trend in the carotenoid composition of green algal lichens was also observed in those species which were found predominantly either in the shade or in full sunlight. In this case sun-exposed lichens often possessed lower levels of zeaxanthin and of the components of the xanthophyll cycle than lichens which were found in the shade. In contrast to higher plants, the lichens from all habitats exhibited a relatively high ratio of carotenoids to chlorophylls (more characteristic of sun leaves), very low levels of α-carotene (similar to that found in sun leaves), and a level of β-carotene similar to that found in shade leaves. Zeaxanthin, but not the expoxides of the xanthophyll cycle, was also frequently found in blue-green algal lichens. A trend for increasing levels of zeaxanthin with increasing growth light regime was observed inPeltigera rufescens, the species which was found to occur over the widest range of light environments. The level of zeaxanthin per chlorophylla in these blue-green algal lichens was in a range similar to that per chlorophylla+b in green algal lichens. However, zeaxanthin was also absent in one species,Collema cristatum, in full sunlight. Thus, the zeaxanthin content of the blue-green algal lichens can be similar to that of higher plants, or it can be rather dissimilar, as was also the case in the green algal lichen species. The presence of large amounts of ketocarotenoids in blue-green algal lichens is also noteworthy.     

Nitrogen fixation in the sub-Antarctic Macquarie Island

Summary The N₂-fixing biota of Macquarie Island are dominated by cyanobacteria growing epiphytically or symbolically with plants or lichens. Highest rates of C₂H₂-reducing activity were found in the leafy lichen Peltigera sp. colonizing herbfields and short grasslands and in the coastal angiosperm Colobanthus muscoides. Significant rates of C₂H₂ reduction were also found to be associated with the liverwort Jamesoniella colorata, commonly occurring in coastal and plateau mires, in a mossbed of Dicranella cardotii colonizing a land-slip face on the grassland slopes at 100 m altitude and within polsters of the mosses Ditrichum strictum and Andreaea sp. found in exposed localities on the plateau at 200–300 m altitude. It was concluded that the common feature of plants supporting active N₂ fixation in dry habitats was the dense packing of stems and leaves, enabling water translocation to the cyanobacterial zone by wick action. Epiphytic cyanobacterial C₂H₂ reduction in wet habitats was widespread and not restricted to any particular plant species. Notable N₂-fixing lichens of the plateau were Pseudocyphellaria delisea and Stereocaulon sp., although both were also occasionally found in coastal herbfields. No significant N₂-fixing activity was associated with any of the dominant grasses tested. Heterotrophic N₂ fixation was also found to be insignificant in the various habitats tested, however N₂-fixing Bacillus (B. macerans or B. polymyxa) were universally present in coastal, grassland slope, or plateau samples, including moss polster samples. A N₂fixing Clostridium sp. was isolated in only one instance, from soil in the vicinity of a seal wallow on the coast.     

RATE OF PHOTOSYNTHESIS AND RESPIRATION IN DIFFERENT LICHEN TISSUES BY THE CARTESIAN DIVER TECHNIQUE

The Cartesian diver technique has been used for measuring respiration in Protozoa, small crustaceans, insects, and in animal tissue; it can also be used to measure both respiration and photosynthesis in unicellular plants and in plant tissues. In two lichens, Peltigera canina and Evernia prunastri, algal-containing tissues were more than 2½ times as active metabolically as medulla. In Peltigera, cortex was slightly more active, rhizines about equally active, and apothecia about a tenth as active as medulla. Light compensation point and peak rates of apparent photosynthesis were reached at higher light intensities in Evernia than in Peltigera. In both lichens, light seemed to retard respiration in the medulla.     

Factors influencing the distribution of aquatic plant communities in Irish canals

Terrestrial tardigrades are often found in the lichens and mosses growing on trees and rocks. The assertion that tardigrades in these habitats are very patchy in their distribution has rarely been backed by quantitative sampling. This study assesses spatial variability in tardigrade populations inhabiting small patches (0.1 cm² to over 5 cm²) of moss and lichen on trees and rocks at three sites in the United States of America. Tardigrades were collected from four replicate rocks in the Ouachita Mountains of Arkansas, with 30 lichen patches collected on two adjacent boulders and 20 moss patches on a second pair of boulders. In Fort Myers and in Citrus Springs, Florida, 30 lichen patches per tree were collected from two pairs of trees. The tardigrades in each sample were extracted, mounted, identified, and counted. The variation in tardigrade abundance among lichen or moss patches within rocks or trees was very high; the only consistent pattern was that very small patches usually lacked tardigrades. Tardigrade diversity and abundance also varied greatly within sites when lichens and mosses of the same species from different rocks and trees were compared (in the most extreme case one tree had numerous individuals of two tardigrade species present while the other had almost no tardigrades). The results of this quantitative sampling support the assertion that tardigrades are very patchy in distribution. Given the considerable time investment required for the quantitative processing of tardigrade samples, this high spatial variability in tardigrade diversity and abundance requires that researches testing ecological hypotheses about tardigrade abundance check variability before deciding how many samples to take.     

Lichen communities and the associated fauna on a rocky sea shore on Bornholm in the Baltic

Thirty-three sampling sites representing 11 lichen dominated plant communities on maritime rocks on Bornholm were analysed with respect to composition of the vegetation, number of animals present and gross taxonomic composition of the fauna. The specific fauna of one moss and seven lichen species was examined.
The lichen communities studied were largely the same as those found in similar studies in NW Europe, except for the recognition of a distinct Ramalina cuspidata community. The highest average number of animals per area was found in the Schistidium maritimum and the Ramalina siliquosa communities, whereas the highest average number of animals g⁻¹ dry plant biomass was recorded in the Parmelia saxatilis community. Among the species examined Anaptychia fusca contained the highest average number of animals g⁻¹ dry thallus and Ramalina cuspidata the lowest number, 114 and 7, respectively. Collemboles appeared to dominate in the moss Schistidium maritimum and in foliose lichens, whereas mites dominated in crustose and fruticose lichens.     

Estimating plant abundance using inflated beta distributions: Applied learnings from a lichen–caribou ecosystem

Quantifying abundance and distribution of plant species can be difficult because data are often inflated with zero values due to rarity or absence from many ecosystems. Terrestrial fruticose lichens (Cladonia and Cetraria spp.) occupy a narrow ecological niche and have been linked to the diets of declining caribou and reindeer populations (Rangifer tarandus) across their global distribution, and conditions related to their abundance and distribution are not well understood. We attempted to measure effects related to the occupancy and abundance of terrestrial fruticose lichens by sampling and simultaneously modeling two discrete conditions: absence and abundance. We sampled the proportion cover of terrestrial lichens at 438 vegetation plots, including 98 plots having zero lichens. A zero‐inflated beta regression model was employed to simultaneously estimate both the absence and the proportion cover of terrestrial fruticose lichens using fine resolution satellite imagery and light detection and ranging (LiDAR) derived covariates. The probability of lichen absence significantly increased with shallower groundwater, taller vegetation, and increased Sphagnum moss cover. Vegetation productivity, Sphagnum moss cover, and seasonal changes in photosynthetic capacity were negatively related to the abundances of terrestrial lichens. Inflated beta regression reliably estimated the abundance of terrestrial lichens (R² = .74) which was interpolated on a map at fine resolution across a caribou range to support ecological conservation and reclamation. Results demonstrate that sampling for and simultaneously estimating both occupancy and abundance offer a powerful approach to improve statistical estimation and expand ecological inference in an applied setting. Learnings are broadly applicable to studying species that are rare, occupy narrow niches, or where the response variable is a proportion value containing zero or one, which is typical of vegetation cover data.     

Phototolerance of lichens, mosses and higher plants in an alpine environment: analysis of photoreactions

 Adaptation to excessive light is one of the requirements of survival in an alpine environment particularly for poikilohydric organisms which in contrast to the leaves of higher plants tolerate full dehydration. Changes in modulated chlorophyll fluorescence and 820-nm absorption were investigated in the lichens Xanthoria elegans (Link) Th. Fr. and Rhizocarpon geographicum (L.) DC, in the moss Grimmia alpestris Limpr. and the higher plants Geum montanum L., Gentiana lutea L. and Pisum sativum L., all collected at altitudes higher than 2000 m above sea level. In the dehydrated state, chlorophyll fluorescence was very low in the lichens and the moss, but high in the higher plants. It increased on rehydration in the lichens and the moss, but decreased in the higher plants. Light-induced charge separation in photosystem II was indicated by pulse-induced fluorescence increases only in dried leaves, not in the dry moss and dry lichens. Strong illumination caused photodamage in the dried leaves, but not in the dry moss and dry lichens. Light-dependent increases in 820-nm absorption revealed formation of potential quenchers of chlorophyll fluorescence in all dehydrated plants, but energy transfer to quenchers decreased chlorophyll fluorescence only in the moss and the lichens, not in the higher plants. In hydrated systems, coupled cyclic electron transport is suggested to occur concurrently with linear electron transport under strong actinic illumination particularly in the lichens because far more electrons became available after actinic illumination for the reduction of photo-oxidized P700 than were available in the pool of electron carriers between photosystems II and I. In the moss Grimmia, but not in the lichens or in leaves, light-dependent quenching of chlorophyll fluorescence was extensive even under nitrogen, indicating anaerobic thylakoid acidification by persistent cyclic electron transport. In the absence of actinic illumination, acidification by ca. 8% CO₂ in air quenched the initial chlorophyll fluorescence yield F_o only in the hydrated moss and the lichens, not in leaves of the higher plants. Under the same conditions, 8% CO₂ reduced the maximal fluorescence yield F_m strongly in the poikilohydric organisms, but only weakly or not at all in leaves. The data indicate the existence of deactivation pathways which enable poikilohydric organisms to avoid photodamage not only in the hydrated but also in the dehydrated state. In the hydrated state, strong nonphotochemical quenching of chlorophyll fluorescence indicated highly sensitive responses to excess light which facilitated the harmless dissipation of absorbed excitation energy into heat. Protonation-dependent fluorescence quenching by cyclic electron transport, P700 oxidation and, possibly, excitation transfer between the photosystems were effectively combined to produce phototolerance. Received: 10 December 1999 / Accepted: 13 April 2000     

Metabolic recovery of continental antarctic cryptogams after winter

The activation of metabolism after the winter period was investigated in several mosses and lichens in continental Antarctica. Thalli that were still in their over-wintering inactive state in early spring were sprayed artificially and the time-dependent activation of photosystem II (PSII), carbon fixation and respiration was determined using gas exchange and chlorophyll a fluorescence techniques. The investigated lichens recovered PSII activity almost completely within the first few minutes and gross photosynthesis was fully reactivated within a few hours. In contrast, photosynthesis took much longer to recover in mosses, which could indicate a general difference between the green-algal symbionts in lichens and moss chloroplasts. Only small and quickly reversible increased rates of respiration were observed for the foliose lichen Umbilicaria aprina from a more xeric habitat. In contrast, species occurring near persistent meltwater, such as the moss Bryum subrotundifolium and the lichen Physcia caesia, had highly increased respiration rates that were maintained for several days after activation. Calculation of the carbon balances indicated that the activation pattern strongly dictated the length of time before a carbon gain was achieved. It appears that the differences in recovery reflect the water relations of the main growth period in summer.     

Multi‐scale patterns of moss and lichen richness on the Antarctic Peninsula

Mosses and lichens are the dominant macrophytes of the Antarctic terrestrial ecosystem. Using occurrence data from existing databases and additional published records, we analyzed patterns of moss and lichen species diversity on the Antarctic Peninsula at both a regional scale (1°latitudinal bands) and a local scale (52 and 56 individual snow‐ and ice‐free coastal areas for mosses and lichens, respectively) to test hypothesized relationships between species diversity and environmental factors, and to identify locations whose diversity may be particularly poorly represented by existing collections and online databases. We found significant heterogeneity in sampling frequency, number of records collected, and number of species found among analysis units at the two spatial scales, and estimated species richness using projected species accumulation curves to account for potential biases stemming from sample heterogeneity. Our estimates of moss and lichen richness for the entire Antarctic Peninsula region were within 20% of the total number of known species. Area, latitude, spatial isolation, mean summer temperature, and penguin colony size were considered as potential covariates of estimated species richness. Moss richness was correlated with isolation and latitude at the local scale, while lichen richness was correlated with summer mean temperature and, for 17 sites where penguins where present with <20 000 breeding pairs, penguin colony size. At the regional scale, moss richness was correlated with temperature and latitude. Lichen richness, by contrast, was not significantly correlated with any of the variables considered at the regional scale. With the exception of temperature, which explained 91% of the variation in regional moss diversity, explained variance was very low. Our results show that patterns of moss and lichen biodiversity are highly scale‐dependent and largely unexplained by the biogeographic variables found important in other systems.     

Stable isotopes of Lithosiini and lichens in Hong Kong show the biodindicator potential of lichenivorous moths

Urban landscapes provide unique environments for a wide variety of plants and animals, but their suitability may be limited by anthropogenic impacts such as pollution. We examined the potential utility of lichen and lichen-feeding moths as biodindicators of air pollution in Hong Kong by comparing carbon (C) and nitrogen (N) stable isotope values in lichens, lichenivorous and non-lichenivorous moths (Lepidoptera: Erebidae) and a moth outgroup (Lepidoptera: Geometridae). Our results show that stable isotope values for C and N were similar for lichens and lichen feeding moths, while non-lichen feeding moths formed a distinct group. In addition, we found consistent δ¹³C and δ¹⁵N values across moth body parts, indicating that any portion of the specimen is suitable for isotopic fingerprinting. Our results highlight that lichen feeding moths may be useful for integrating signals of atmospheric nitrogen pollution and could therefore have utility in monitoring and quantifying air quality over time and space.     

As thick as three in a bed

During the evolution of the lichen symbiosis, shifts from one main type of photobiont to another were infrequent (Miadlikowska et al. 2006 ) but some remarkable transitions from green algal to diazotrophic cyanobacterial photobionts are known from unrelated fungal clades within the ascomycetes. Cyanobacterial, including tripartite, associations (green algal and cyanobacterial photobionts in one lichen individual) facilitate these holobionts to live as C‐ and N‐autotrophs. Tripartite lichens are among the most productive lichens, which provide N‐fertilization to forest ecosystems under oceanic climates (Peltigerales) or deliver low, but ecologically significant N‐input into subarctic and alpine soil communities (Lecanorales, Agyriales). In this issue of Molecular Ecology, Schneider et al. (2016) mapped morphometric data against an eight‐locus fungal phylogeny across a transition of photobiont interactions from green algal to a tripartite association and used a phylogenetic comparative framework to explore the role of nitrogen‐fixing cyanobacteria in size differences in the Trapelia–Placopsis clade (Agyriales). Within the group of tripartite species, the volume of cyanobacteria‐containing structures (cephalodia) correlates with thallus thickness in both phylogenetic generalized least squares and phylogenetic generalized linear mixed‐effects analyses, and the fruiting body core volume increased ninefold. The authors conclude that cyanobacterial symbiosis appears to have enabled lichens to overcome size constraints in oligotrophic environments such as rock surfaces. The Trapelia–Placopsis clade analyzed by Schneider et al. (2016) is an exciting example of interactions between ecology, phylogeny and lichen biology including development – from thin crustose green algal microlichens to thick placodioid, tripartite macrolichens: as thick as three in a bed (Scott 1820 ).     

Lichens and mosses promote alternate stable plant communities in the New Jersey Pinelands

Severely burned areas in the pitch pine-dominated forests of the New Jersey Pinelands may remain open and only vegetated with mats of lichens and mosses and sparse, scattered vascular plants for many decades. We hypothesize that climate-driven alternation between moss and lichen domination of the cryptogam mats may foster and inhibit, respectively, vascular plant development. We propose that these processes are mediated by the inhibitory effects of lichens on seed germination and seedling establishment versus a facilitating effect of mosses. We tested the hypothesis by 1) detailed surveys of the composition of cryptogam mats and their association with vascular plants, 2) experimental studies of the effects of tissue leachates on seed germination, 3) observations of mycorrhizal infection in field-collected plants, and 4) experimental tests of seedling emergence from mats. Lichen dominance in the mats was correlated with low densities of vascular plants (graminoids and ericoid shrubs), thin organic horizons on the soil, and high levels of light availability; moss dominance was correlated with higher vascular plant densities, thicker organic horizons, and lower light. Tissue extracts of lichens strongly inhibited seed germination, while moss extracts had no effect. Similarly, mycorrhizal infection by both ecto- and endomycorrhizae was lower in plants growing within lichen mats than in moss mats or in bare soil. However, thick mats of both types of cryptogam inhibited seedling emergence. We observed that moss-dominated patches became overgrown with lichens during a series of very dry, hot summers during the study. These observations all support the hypothesis that fluctuating warm and dry versus cool and moist conditions allow alternative stable states (open cryptogam mats vs succession to pine forest) to develop.     

NudC Nudix hydrolase from Pseudomonas syringae,but not its counterpart from Pseudomonas aeruginosa,is a novel regulator of intracellular redox balance required for growth,motility and biofilm formation

Nudix pyrophosphatases, ubiquitous in all organisms, have not been well studied. Recent implications that some of them may be involved in response to stress and in pathogenesis indicate that they play important biological functions. We have investigated NudC Nudix proteins from the plant pathogen Pseudomonas syringae pv. tomato str. DC3000 and from the human pathogen Pseudomonas aeruginosa PAO1161. We found that these homologous enzymes are homodimeric and in vitro preferentially hydrolyse NADH. The P. syringae mutant strain deficient in NudC accumulated NADH and displayed significant defects in growth, motility and biofilm formation. The wild type copy of the nudC gene with its cognate promoter delivered in trans into the nudC mutant restored its fitness. However, introduction of the P. syringae nudC gene under the control of the strong tacp promoter into either P. syringae or P. aeruginosa cells had a toxic effect on both strains. Opposite to P. syringae NudC, the P. aeruginosa NudC deficiency as well as its overproduction had no visible impact on cells. Moreover, P. aeruginosa NudC does not compensate the lack of its counterpart in the P. syringae mutant. These results indicate that NudC from P. syringae, but not from P. aeruginosa is vital for bacteria.     

Lipid and Fatty Acid Composition of Tree-Growing and Terrestrial Lichens

A comparison of lipid and fatty acid composition was made of the tree-growing lichens Evernia prunastri (L.) Ach., Parmelia saxatilis (L.) Ach. and Hypogymnia physodes (L.) Ach. and the terrestrial species Cetraria islandica (L.) Ach. and Cladonia impexa Harm. In the terrestrial species the total lipid content varied strongly during spring, while the tree-growing species showed much less variation. Phospholipid and sterol content of all lichens was unusually low. Monoglycosyl diglyceride was absent from Parmelia saxatilis. Fatty acids common to higher plants as palmitic, stearic, oleic, linoleic and linolenic acid were invariably present in all lichen species. In addition large quantities of extra-long chain fatty acids like behenic acid, eicosadienoic acid and cyclic aliphatic lichen acids were present in the terrestrial species. The degree of (poly) unsaturation decreased in the order Evernia prunastri, Parmelia saxatilis. Fatty acids common to higher plants as palmitic, stearic, impexa, which decrease was compensated by an increase in extralong chain fatty acids and lichen acids. It is suggested that the lichen acids are of adaptive value for lichen species growing in the terrestrial habitats, which were characterized by extreme diurnal temperature variations. Just as the polyunsaturated fatty acids, lichen acids guarantee at lower temperatures a high flexibility of the membranes involved, at the same time as they are less susceptible to photo-oxidation at the high daytime temperatures.