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  • 1
    ISSN: 1432-0983
    Keywords: Keywords Ribosomal DNA ; Small subunit ; 18s ; Degenerate introns ; Ascomycetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Insertions of less than 100 nt occurring in highly conserved regions of the small subunit ribosomal DNA (SSU rDNA) may represent degenerate forms of the group-I introns observed at the same positions in other organisms. A 63-nt insertion at SSU rDNA position 1512 (relative to the Escherichia coli SSU rDNA) of the lichen-forming fungus Arthonia lapidicola can be folded into a secondary structure with two stem loops and a pairing of the insertion and flanking sequences. The two stem loops may correspond to the P1 and P2, and the insertion-flanking pairing to the P10, of a group-I intron. Considering these small insertions as degenerate introns provides important clues to the evolution and catalytic function of group-I introns.
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  • 2
    ISSN: 1432-0983
    Keywords: Ribosomal DNA ; Small subunit ; 18s ; Degenerate introns ; Ascomycetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Insertions of less than 100 nt occurring in highly conserved regions of the small subunit ribosomal DNA (SSU rDNA) may represent degenerate forms of the group-I introns observed at the same positions in other organisms. A 63-nt insertion at SSU rDNA position 1512 (relative to theEscherichia coli SSU rDNA) of the lichen-forming fungusArthonia lapidicola can be folded into a secondary structure with two stem loops and a pairing of the insertion and flanking sequences. The two stem loops may correspond to the P1 and P2, and the insertion-flanking pairing to the P10, of a group-I intron. Considering these small insertions as degenerate introns provides important clues to the evolution and catalytic function of group-I introns.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Fatty acid components, in both the free and combined form of the intact tropical lichen Teloschistes flavicans, and its isolated photobiont and mycobiont, were analyzed by GC-MS of derived methyl esters. Its rDNA analysis confirmed that the isolated cultured symbionts belong to the genera Trebouxia and Teloschistes, respectively. The fatty acid composition of the lichen did not correspond to those found in the isolated symbionts, suggesting that the fatty acid metabolism is markedly influenced by the symbiosis. Differences in the fatty acid composition in the lichen were observed during the summer (27°C), when the main fatty acids were saturated and in the winter (22°C) when an increase of unsaturated fatty acids occurred. Similar differences of composition were also observed for the cultured mycobiont at different temperatures. The increase in the unsaturation level at low temperatures would maintain the membrane fluidity. Our results are the first on the fatty acids of a tropical lichen and suggest that it is sensitive to small temperature variations, which influences its saturated and unsaturated fatty acid composition.
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  • 4
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A light microscopic and molecular analysis of photobionts in Ramalina and Cladonia from coastal habitats of Brazil is presented. A Bayesian phylogenetic analysis of ITS rDNA sequences suggests a Trebouxia lineage which is preferentially tropical in geographic distribution. This highly diverse clade also includes the morphological similar species Trebouxia higginsiae and galapagensis. Within the predominantly tropical clade of Trebouxia we distinguish several subclades, three of which are represented in our samples of Ramalina species. Since sexuality has not been recognized in coccal lichenised photobionts until recently, we cannot apply a biological species concept, but when compared with the sequence diversity between known species we conclude that several new species need to be described in this clade. The mutually exclusive presence of other Trebouxia lineages in temperate samples of Ramalina suggests an evolution towards higher selectivity in this genus. A strictly tropical lineage is not conspicuous in the photobionts of the genus Asterochloris sampled from Cladonia so far.
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  • 5
    Publication Date: 2020-02-06
    Description: The microbial diversity and function of terrestrial lichens have been well studied, but knowledge about the non-photosynthetic bacteria associated with marine lichens is still scarce. 16S rRNA gene Illumina sequencing was used to assess the culture-independent bacterial diversity in the strictly marine cyanolichen species Lichina pygmaea and Lichina confinis, and the maritime chlorolichen species Xanthoria aureola which occupy different areas on the littoral zone. Inland terrestrial cyanolichens from Austria were also analysed as for the marine lichens to examine further the impact of habitat/lichen species on the associated bacterial communities. The L. confinis and L. pygmaea communities were significantly different from those of the maritime Xanthoria aureola lichen found higher up on the littoral zone and these latter communities were more similar to those of the inland terrestrial lichens. The strictly marine lichens were dominated by the Bacteroidetes phylum accounting for 50% of the sequences, whereas Alphaproteobacteria, notably Sphingomonas, dominated the maritime and the inland terrestrial lichens. Bacterial communities associated with the two Lichina species were significantly different sharing only 33 core OTUs, half of which were affiliated to the Bacteroidetes genera Rubricoccus, Tunicatimonas and Lewinella, suggesting an important role of these species in the marine Lichina lichen symbiosis. Marine cyanolichens showed a higher abundance of OTUs likely affiliated to moderately thermophilic and/or radiation resistant bacteria belonging to the Phyla Chloroflexi, Thermi, and the families Rhodothermaceae and Rubrobacteraceae when compared to those of inland terrestrial lichens. This most likely reflects the exposed and highly variable conditions to which they are subjected daily.
    Type: Article , PeerReviewed
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  • 6
  • 7
    Publication Date: 2020-02-06
    Description: Alphaproteobacterium strain MOLA1416, related to Mycoplana ramosa DSM 7292 and Chelativorans intermedius CC-MHSW-5 (93.6% 16S rRNA sequence identity) was isolated from the marine lichen, Lichina pygmaea and its chemical composition was characterized by a metabolomic network analysis using LC-MS/MS data. Twenty-five putative different compounds were revealed using a dereplication workflow based on MS/MS signatures available through GNPS (https://gnps.ucsd.edu/). In total, ten chemical families were highlighted including isocoumarins, macrolactones, erythrinan alkaloids, prodiginines, isoflavones, cyclohexane-diones, sterols, diketopiperazines, amino-acids and most likely glucocorticoids. Among those compounds, two known metabolites (13 and 26) were isolated and structurally identified and metabolite 26 showed a high cytotoxic activity against B16 melanoma cell lines with an IC50 0.6 ± 0.07 μg/mL.
    Type: Article , PeerReviewed
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  • 8
    Publication Date: 2017-12-21
    Description: Cultivable Actinobacteria are the largest source of microbially derived bioactive molecules. The high demand for novel antibiotics highlights the need for exploring novel sources of these bacteria. Microbial symbioses with sessile macro-organisms, known to contain bioactive compounds likely of bacterial origin, represent an interesting and underexplored source of Actinobacteria. We studied the diversity and potential for bioactive-metabolite production of Actinobacteria associated with two marine lichens ( Lichina confinis and L. pygmaea ; from intertidal and subtidal zones) and one littoral lichen ( Roccella fuciformis ; from supratidal zone) from the Brittany coast (France), as well as the terrestrial lichen Collema auriforme (from a riparian zone, Austria). A total of 247 bacterial strains were isolated using two selective media. Isolates were identified and clustered into 101 OTUs (98% identity) including 51 actinobacterial OTUs. The actinobacterial families observed were: Brevibacteriaceae, Cellulomonadaceae, Gordoniaceae, Micrococcaceae, Mycobacteriaceae, Nocardioidaceae, Promicromonosporaceae, Pseudonocardiaceae, Sanguibacteraceae and Streptomycetaceae. Interestingly, the diversity was most influenced by the selective media rather than lichen species or the level of lichen thallus association. The potential for bioactive-metabolite biosynthesis of the isolates was confirmed by screening genes coding for polyketide synthases types I and II. These results show that littoral lichens are a source of diverse potentially bioactive Actinobacteria.
    Type: Article , PeerReviewed
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  • 9
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    In:  In: Ecophysiology and Responses of Plants under Salt Stress. UNSPECIFIED, pp. 115-148.
    Publication Date: 2018-03-15
    Description: Lichens are among the most conspicuous and ubiquitous symbiosis on this planet. They are highly adapted to terrestrial habitats of all climatic zones including the most hostile environments on Earth, such as high altitudes in the Himalayas or the cold deserts of Antarctica. Among the extreme habitats are the littoral (or intertidal) zones of coasts. In this chapter, we present an overview of the current knowledge about the halotolerance mechanisms in lichens. Halotolerant organisms generally accumulate osmotically active solutes to cope with increasing external salinity. In intertidal lichens, mannitol could play an important role in osmoregulation. Epilichenic bacterial colonies may be also involved in limiting lichen nutrient imbalance by producing osmoprotective compounds and storing high ionic concentrations. In addition, the comparison with related inland species suggests that morphological adaptations could also be involved in adaptation to increased salt levels. Maritime species often have strongly conglutinated hyphae and small or no intercellular spaces in their thalli. So far, little genetic information exists about the genes involved in halotolerance and their regulation. Comparison of forthcoming genomic information from lichen fungi with those of other halotolerant fungi will soon help to change the picture and reveal genetic adaptations to saline environments.
    Type: Book chapter , PeerReviewed
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  • 10
    Publication Date: 2019-02-01
    Description: This review presents the state of knowledge on the medicinal potential of bacteria associated with lichens. In fact, besides the classical symbiotic partners (photobiont and mycobiont) forming the lichen thallus, associated bacteria have been recently described as a third partner. Various studies demonstrated the diversity of these communities with a predominance of Alphaproteobacteria. Bacterial groups more relevant for secondary metabolite synthesis have also been revealed. This article summarizes studies reporting the abilities of these communities to produce metabolites with relevant bioactivities. The biotechnological interest of these bacteria for drug discovery is highlighted regarding the production of compounds with therapeutic potential. Special focus is given to the synthesis of the most promising compound, uncialamycin, a potent enediyne isolated from a Streptomyces sp. associated with Cladonia uncialis.
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