title: Potential and limits of Raman spectroscopy for carotenoid detection in microorganisms: implications for astrobiology.
abstract: In this paper, it is demonstrated how Raman spectroscopy can be used to detect different carotenoids as possible biomarkers in various groups of microorganisms. The question which arose from previous studies concerns the level of unambiguity of discriminating carotenoids using common Raman microspectrometers. A series of laboratory-grown microorganisms of different taxonomic affiliation was investigated, such as halophilic heterotrophic bacteria, cyanobacteria, the anoxygenic phototrophs, the non-halophilic heterotrophs as well as eukaryotes (Ochrophyta, Rhodophyta and Chlorophyta). The data presented show that Raman spectroscopy is a suitable tool to assess the presence of carotenoids of these organisms in cultures. Comparison is made with the high-performance liquid chromatography approach of analysing pigments in extracts. Direct measurements on cultures provide fast and reliable identification of the pigments. Some of the carotenoids studied are proposed as tracers for halophiles, in contrast with others which can be considered as biomarkers of other genera. The limits of application of Raman spectroscopy are discussed for a few cases where the current Raman spectroscopic approach does not allow discriminating structurally very similar carotenoids. The database reported can be used for applications in geobiology and exobiology for the detection of pigment signals in natural settings.
authors.affiliation: Institute of Geochemistry, Mineralogy and Mineral Resources, Charles University in Prague, Albertov 6, 12843 Prague, Czech Republic jehlička@natur.cuni.cz.
authors.forename: Jan
authors.initials: J
authors.lastname: Jehlička
authors.affiliation: Centre for Astrobiology and Extremophiles Research, University of Bradford, Bradford BD7 1DP, UK.
authors.forename: Howell G M
authors.initials: HG
authors.lastname: Edwards
authors.affiliation: Institute of Geochemistry, Mineralogy and Mineral Resources, Charles University in Prague, Albertov 6, 12843 Prague, Czech Republic.
authors.forename: Kateřina
authors.initials: K
authors.lastname: Osterrothová
authors.affiliation: Institute of Geochemistry, Mineralogy and Mineral Resources, Charles University in Prague, Albertov 6, 12843 Prague, Czech Republic.
authors.forename: Julie
authors.initials: J
authors.lastname: Novotná
authors.affiliation: Department of Ecology, Charles University in Prague, Viničná 7, 12844 Prague, Czech Republic.
authors.forename: Linda
authors.initials: L
authors.lastname: Nedbalová
authors.affiliation: Academy of Science of the Czech Republic, Institute of Microbiology, Třeboň, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Kopecký
authors.affiliation: Department of Inorganic Chemistry, Charles University in Prague, Hlavova 8, 12843 Prague, Czech Republic.
authors.forename: Ivan
authors.initials: I
authors.lastname: Němec
authors.affiliation: Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat-Ram, Jerusalem 91904, Israel.
authors.forename: Aharon
authors.initials: A
authors.lastname: Oren
keywords: Raman spectroscopy; algae; bacteria; cyanobacteria; detecting carotenoids; high-performance
  liquid chromatography