title: In vivo NMR metabolic profiling of Fabrea salina reveals sequential defense mechanisms against ultraviolet radiation.
abstract: Fabrea salina is a hypersaline ciliate that is known to be among the strongest ultraviolet (UV)-resistant microorganisms; however, the molecular mechanisms of this resistance are almost unknown. By means of in vivo NMR spectroscopy, we determined the metabolic profile of living F. salina cells exposed to visible light and to polychromatic UV-B + UV-A + Vis radiation for several different exposure times. We used unsupervised pattern-recognition analysis to compare these profiles and discovered some metabolites whose concentration changed specifically upon UV exposure and in a dose-dependent manner. This variation was interpreted in terms of a two-phase cell reaction involving at least two different pathways: an early response consisting of degradation processes, followed by a late response activating osmoprotection mechanisms. The first step alters the concentration of formate, acetate, and saturated fatty-acid metabolites, whereas the osmoprotection modifies the activity of betaine moieties and other functionally related metabolites. In the latter pathway, alanine, proline, and sugars suggest a possible incipient protein synthesis as defense and/or degeneration mechanisms. We conclude that NMR spectroscopy on in vivo cells is an optimal approach for investigating the effect of UV-induced stress on the whole metabolome of F. salina because it minimizes the invasiveness of the measurement.
authors.affiliation: Dipartimento di Informatica, Università di Pisa, Pisa, Italy. marangon@di.unipi.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Marangoni
authors.forename: Debora
authors.initials: D
authors.lastname: Paris
authors.forename: Dominique
authors.initials: D
authors.lastname: Melck
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Fulgentini
authors.forename: Giuliano
authors.initials: G
authors.lastname: Colombetti
authors.forename: Andrea
authors.initials: A
authors.lastname: Motta
mesh_terms: D016798:Ciliophora / Q000276:immunology* / Q000378:metabolism* / Q000528:radiation effects; D009682:Magnetic Resonance Spectroscopy; D055442:Metabolome / Q000528:radiation effects*; D025341:Principal Component Analysis; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays