Article

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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    • "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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    • "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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