Mycosporine-glutamicol-glucoside: A natural UV-absorbing secondary metabolite of rock-inhabiting microcolonial fungi

Department of Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky Universität Oldenburg, Oldenburg, Lower Saxony, Germany
Rapid Communications in Mass Spectrometry (Impact Factor: 2.64). 08/2006; 17(9):897-902. DOI: 10.1002/rcm.997
Source: PubMed

ABSTRACT Microcolonial ascomycetes are known to inhabit bare rock surfaces in cold and hot deserts and thus are habitually exposed to high levels of solar radiation. Several of these stress-tolerant fungal isolates, cultivated in the laboratory under daylight illumination, were studied for the presence of effective UV-radiation protection substances. Liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) analyses allowed for efficient separation and structure clarification of two mycosporines. It was demonstrated that both mycosporine-glutamicol-glucoside and mycosporine-glutaminol-glucoside are natural and constitutive secondary metabolites of microcolonial fungi. The function and relation of these substances in the fungal cell are discussed.

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    • "Whole colonies can, in fact, be " mummified " (Gorbushina et al. 2002). Fungi in subaerial rock environments—like hot and cold deserts with varying extremes in microclimatic conditions including irradiation, salinity, pH, humidity and temperature— protect themselves by producing extracellular polymeric substances (EPS) and/or mucilaginous polysaccharides that contain clay particles (Gorbushina 2003; Volkmann et al. 2003; Gadd 2007). Under extreme conditions, whole colonies can be embedded in such clay-containing mucilaginous precipitates. "
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    ABSTRACT: The deep subseafloor crust is one of the few great frontiers of unknown biology on Earth and, still today, the notion of the deep biosphere is commonly based on the fossil record. Interpretation of palaeobiological information is thus central in the exploration of this hidden biosphere and, for each new discovery, criteria used to establish biogenicity are challenged and need careful consideration. In this paper networks of fossilized filamentous structures are for the first time described in open fractures of subseafloor basalts collected at the Emperor Seamounts, Pacific Ocean. These structures have been investigated with optical microscopy, environmental scanning electron microscope, energy dispersive spectrometer, X-ray powder diffraction as well as synchrotron-radiation X-ray tomographic microscopy, and interpreted as fossilized fungal mycelia. Morphological features such as hyphae, yeast-like growth and sclerotia were observed. The fossilized fungi are mineralized by montmorillonite, a process that probably began while the fungi were alive. It seems plausible that the fungi produced mucilaginous polysaccharides and/or extracellular polymeric substances that attracted minerals or clay particles, resulting in complete fossilization by montmorillonite. The findings are in agreement with previous observations of fossilized fungi in subseafloor basalts and establish fungi as regular inhabitants of such settings. They further show that fossilized microorganisms are not restricted to pore spaces filled by secondary mineralizations but can be found in open pore spaces as well. This challenges standard protocols for establishing biogenicity and calls for extra care in data interpretation.
    Geo-Marine Letters 08/2013; 33(4). DOI:10.1007/s00367-013-0321-7 · 2.06 Impact Factor
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    • "Mycosporines have also been assigned a photoprotective role in aquatic yeasts, isolated from different freshwater bodies (Libkind et al., 2004). The synthesis of the mycosporine-glutaminol-glucoside (Volkmann et al., 2003) was dramatically stimulated in the presence of photosynthetically active radiation and UV radiation, suggesting a photoprotective function (Libkind et al., 2004). The high concentrations of mycosporine-glutaminol-glucoside observed in the two Rhodotorula species (up to 0.5% of the dry weight) after induction with UV radiation supports the idea that the synthesis of this secondary metabolite is important to obtain protection from UV stress. "
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    ABSTRACT: Mycosporines and mycosporine-like amino acids (MAAs) are low-molecular-weight water-soluble molecules absorbing UV radiation in the wavelength range 310-365 nm. They are accumulated by a wide range of microorganisms, prokaryotic (cyanobacteria) as well as eukaryotic (microalgae, yeasts, and fungi), and a variety of marine macroalgae, corals, and other marine life forms. The role that MAAs play as sunscreen compounds to protect against damage by harmful levels of UV radiation is well established. However, evidence is accumulating that MAAs may have additional functions: they may serve as antioxidant molecules scavenging toxic oxygen radicals, they can be accumulated as compatible solutes following salt stress, their formation is induced by desiccation or by thermal stress in certain organisms, they have been suggested to function as an accessory light-harvesting pigment in photosynthesis or as an intracellular nitrogen reservoir, and they are involved in fungal reproduction. Here, the evidence for these additional roles of MAAs as 'multipurpose' secondary metabolites is reviewed, with special emphasis on their functions in the microbial world.
    FEMS Microbiology Letters 05/2007; 269(1):1-10. DOI:10.1111/j.1574-6968.2007.00650.x · 2.72 Impact Factor
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    • "In addition, organic and inorganic residues on mineral surfaces or within cracks and fissures, waste products of other microorganisms, decaying plants and animals, dust particles, aerosols and animal faeces can also act as nutrient sources in the subaerial rock environment (Sterflinger 2000). Inhabitants of subaerial surfaces include poikilotrophic fungi, which are able to deal with varying extremes in microclimatic conditions , including irradiation, salinity, pH, and water potential, and which protect themselves by producing antioxidant protectors , such as melanins and mycosporines in their in cell walls, and by embedding colonies in mucilaginous polysaccharides that often contains clay particles (Gorbushina et al. 2003; Volkmann et al. 2003). One of the most successful means enabling fungi to survive in the extreme subaerial environment is by means of forming mutualistic symbioses with algae and cyanobacteria as lichens, where the phototrophs provide a source of carbon and are protected to some degree from light and irradiation (Gorbushina et al. 1993; Sterflinger 2000). "
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    Mycological Research 02/2007; 111(Pt 1):3-49. DOI:10.1016/j.mycres.2006.12.001 · 2.81 Impact Factor
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