The effect of the water source on niche partioning of chlorolichens and cyanobacteria-implications for resilience?

MAIN CONCLUSION: Microclimate determines lichens and cyanobacteria distribution in the Negev, with lichens and cyanobacteria inhabit dewy and dewless habitats, respectively. Lichens experiences more frequent and extensive environmental fluctuations than cyanobacteria. The spatial partitioning of chlorolichens (eukaryotes) and cyanobacteria (prokaryotes) are intriguing, especially following recent intense search for extraterrestrial life. This is especially relevant for deserts, where both lithobionts are thought to use rain and dew but may differ in their resilience to environmental extremes and fluctuations. Following the different spatial distribution of lithobionts in a south-facing slope of the Negev Highlands (with cyanobacteria-inhabiting rocks and chlorolichen-inhabiting cobbles), measurements of temperature, non-rainfall water (NRW) and biomass were carried out within the drainage basin aiming to test the hypotheses that (i) cobble-inhabiting lichens may access more water (through NRW) and may be subjected to more extensive environmental fluctuations of temperature and water than bedrock-inhabiting cyanobacteria, and (ii) will therefore have a greater contribution to the ecosystem productivity. In contrast to cyanobacteria, cobble-inhabiting chlorolichens were found to access NRW (up to 0.20 mm of daily amounts in comparison to < 0.04 mm of the cyanobacteria) and to experience higher fluctuations of temperatures (up to 4.1 °C higher and 5.3 °C lower). With lichens and cyanobacteria inhabiting dewy and dewless habitats, respectively, NRW was found responsible for contributing 6.8-fold higher organic carbon to the lithobiontic community. At this site, chlorolichens experience more extensive environmental fluctuations than cyanobacteria, possibly indicating a higher tolerance for environmental fluctuations. These observations may assist in the interpretation of the abiotic conditions responsible for past or present lithobiontic life on Mars.

Metagenomics Shines Light on the Evolution of "Sunscreen" Pigment Metabolism in the Teloschistales (Lichen-Forming Ascomycota).

Fungi produce a vast number of secondary metabolites that shape their interactions with other organisms and the environment. Characterizing the genes underpinning metabolite synthesis is therefore key to understanding fungal evolution and adaptation. Lichenized fungi represent almost one-third of Ascomycota diversity and boast impressive secondary metabolites repertoires. However, most lichen biosynthetic genes have not been linked to their metabolite products. Here we used metagenomic sequencing to survey gene families associated with production of anthraquinones, UV-protectant secondary metabolites present in various fungi, but especially abundant in a diverse order of lichens, the Teloschistales (class Lecanoromycetes, phylum Ascomycota). We successfully assembled 24 new, high-quality lichenized-fungal genomes de novo and combined them with publicly available Lecanoromycetes genomes from taxa with diverse secondary chemistry to produce a whole-genome tree. Secondary metabolite biosynthetic gene cluster (BGC) analysis showed that whilst lichen BGCs are numerous and highly dissimilar, core enzyme genes are generally conserved across taxa. This suggests metabolite diversification occurs via re-shuffling existing enzyme genes with novel accessory genes rather than BGC gains/losses or de novo gene evolution. We identified putative anthraquinone BGCs in our lichen dataset that appear homologous to anthraquinone clusters from non-lichenized fungi, suggesting these genes were present in the common ancestor of the subphylum Pezizomycotina. Finally, we identified unique transporter genes in Teloschistales anthraquinone BGCs that may explain why these metabolites are so abundant and ubiquitous in these lichens. Our results support the importance of metagenomics for understanding the secondary metabolism of non-model fungi such as lichens.

Biodiversity of the chemical constituents in the epiphytic lichenized ascomycete Ramalina lacera grown on difference substrates Crataegus sinaicus, Pinus halepensis, and Quercus calliprinos.

AIM: The identification and evaluation of lichen metabolite production by the epiphytic lichenized ascomycete Ramalina lacera collected from different substrates: Crataegus sinaicus, Pinus halepensis, and Quercus calliprinos. METHODS: Chemical constituents were characterized by GC MS, HPLC, HR TLC, and other chemical methods. RESULTS: The most abundant fatty acids were alpha-linolenic acid, oleic acid, and palmitic acid but a considerable variability of the ester composition from one to another was found. A comparison of neutral lipids, glycolipids, polar lipids and fatty acid composition of the tree growing lichen Ramalina lacera was done. Diacylglyceryl N,N,N trimethylhomoserine, diaclyglycerylhydroxymethyl N,N,N trimethyl beta alanine, phosphatidylcholine, and phosphatidylinositol were found as major components among polar lipids. Diffractaic, lecanoric, norstictic, protocetric, and usnic acids were isolated as major aromatic compounds in all samples of R. lacera. CONCLUSIONS: We evaluated a diversity of fatty acids, lipids, and aromatic compounds produced by the samples of Ramalina lacera growing on different tree substrates, Crataegus sinaicus, Pinus halepensis and Quercus calliprinos.

Diversity of the fatty acids of the Nostoc species and their statistical analysis.

Low molecular, hydroxy, dioic, saturated and unsaturated fatty acids were determined of six cyanobacterial species belonging to genus Nostoc and in different habitats: freshwater, terrestrial, and as well as symbionts. There are large variations in individual fatty acid contents according to species, and location of the genus Nostoc. Statistical analysis of variability of fatty acids belonging to the genus Nostoc is reported.

The tornabeatins, four tetrahydro-2-furanone derivatives from the lichenized ascomycete Tornabea scutellifera (With.) J.R. Laundon.

Tornabeatins A, B, C and D, have been isolated as new natural products from the lichenized ascomycete Tornabea scutellifera, and their structures elucidated using UV, IR, MS, 1D and 2D NMR spectral data and chemical degradation.

A new UV-B absorbing mycosporine with photo protective activity from the lichenized ascomycete Collema cristatum.

A novel photo protective mycosporine was isolated from the lichenized ascomycete Collema cristatum. Biological activity was measured in terms of protection against UV-B induced membrane destruction and pyrimidine dimer formation in cultured human keratinocytes, and prevention of UV-B induced erythema. It was found that the pure isolated compound prevented UV-B induced cell destruction in a dose-dependent manner, that the compound partially prevented pyrimidine dimer formation and completely prevented UV-B induced erythema when applied to the skin prior to irradiation.