title: UV-B-induced synthesis of photoprotective pigments and extracellular polysaccharides in the terrestrial cyanobacterium Nostoc commune.
abstract: Liquid cultures of the terrestrial cyanobacterium Nostoc commune derived from field material were treated with artificial UV-B and UV-A irradiation. We studied the induction of various pigments which are though to provide protection against damaging UV-B irradiation. First, UV-B irradiation induced an increase in carotenoids, especially echinenone and myxoxanthophyll, but did not influence production of chlorophyll a. Second, an increase of an extracellular, water-soluble UV-A/B-absorbing mycosporine occurred, which was associated with extracellular glycan synthesis. Finally, synthesis of scytonemin, a lipid-soluble, extracellular pigment known to function as a UV-A sunscreen, was observed. After long-time exposure, the UV-B effect on carotenoid and scytonemin synthesis ceased whereas the mycosporine content remained constantly high. The UV-B sunscreen mycosporine is exclusively induced by UV-B (< 315 nm). The UV-A sunscreen scytonemin is induced only slightly by UV-B (< 315 nm), very strongly by near UV-A (350 to 400 nm), and not at all by far UV-A (320 to 350 nm). These results may indicate that the syntheses of these UV sunscreens are triggered by different UV photoreceptors.
authors.affiliation: Institut für Mikrobiologie/FML, Technische Universität München, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Ehling-Schulz
authors.forename: W
authors.initials: W
authors.lastname: Bilger
authors.forename: S
authors.initials: S
authors.lastname: Scherer
mesh_terms: D002338:Carotenoids / Q000096:biosynthesis; D000458:Cyanobacteria / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D007211:Indoles / Q000378:metabolism; D010636:Phenols / Q000378:metabolism; D010860:Pigments, Biological / Q000096:biosynthesis*; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D014466:Ultraviolet Rays
chemical_list: D007211:Indoles; D010636:Phenols; D010860:Pigments, Biological; D011135:Polysaccharides, Bacterial; C083368:scytonemin; D002338:Carotenoids