Optimizing the detection of carotene in cyanobacteria in a martian regolith analogue with a Raman spectrometer for the ExoMars mission

Dolomite precipitation, limited at low temperature, appears to be impacted by microbial extracellular polymeric substances (EPS). The presence of dolomites has been reported in the extreme environments of Arabian Gulf sabkhas. Many of these sites are characterized by extensive growth of cyanobacterial mats that are recognized as key producers of EPS. However, no information has been gathered on the cyanobacterial EPS involvement in dolomite precipitation. The objective of this study was to obtain in situ information on the spatial distribution of cyanobacterial EPS and dolomite in Khor Al‐Adaid sabkha (Qatar) sediments by chemical mapping. For this purpose, in situ 2D Raman spectroscopy and atomic force microscopy were applied. Additionally, samples were analyzed with scanning electron microscopy and X‐ray diffraction. Raman fingerprints of dolomite (300, 725, and 1098 cm−1), cyanobacteria, and their EPS (1000, 1130, 1148, and 1508 cm−1) were observed widely distributed in the top 2 cm of the sabkhas sediments. 2D chemical imaging of sediment layers characterized minerals and organic matter of microbial origins at high spatial resolution. Raman mapping indicated small dolomite clusters (<2 µm) embedded in a dense cyanobacterial EPS matrix. The spatial distribution showed that small dolomite clusters are closely associated with cyanobacterial EPS and organic carbon. Our results prove that cyanobacterial molecules are closely related to dolomite in the sabkhas sediments. This study demonstrated that Raman mapping is a robust and sensitive technique for acquisition of in situ information on cell–mineral interactions. Copyright © 2013 John Wiley & Sons, Ltd.

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“…). Similar observations have been made in other sabkhas environments as well as in other environments colonized by cyanobacteria …”

Section: Resultssupporting

confidence: 89%

2D Raman spectroscopy study of dolomite and cyanobacterial extracellular polymeric substances from Khor Al‐Adaid sabkha (Qatar)

Paulo

Dittrich

2013

J Raman Spectroscopy

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“…(b) X-ray diffraction under ambient air of a spot approximately 1.5 µm in diameter using a confocal microscope as in [54]. The excitation wavelength was 532 nm, the laser power ranged between 0.5 and 3 mW, and a 600 lines mm −1 grating was used.…”

Section: Methods (A) Samplesmentioning

confidence: 99%

Mineralogical analyses of surface sediments in the Antarctic Dry Valleys: coordinated analyses of Raman spectra, reflectance spectra and elemental abundances

Bishop

Englert

Patel

et al. 2014

Phil. Trans. R. Soc. A.

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Surface sediments at Lakes Fryxell, Vanda and Brownworth in the Antarctic Dry Valleys (ADV) were investigated as analogues for the cold, dry environment on Mars. Sediments were sampled from regions surrounding the lakes and from the ice cover on top of the lakes. The ADV sediments were studied using Raman spectra of individual grains and reflectance spectra of bulk particulate samples and compared with previous analyses of subsurface and lakebottom sediments. Elemental abundances were coordinated with the spectral data in order to assess trends in sediment alteration. The surface sediments in this study were compared with lakebottom sediments (Bishop JL et al . 2003 Int. J. Astrobiol . 2 , 273–287 ( doi:10.1017/S1473550403001654 )) and samples from soil pits (Englert P et al . 2013 In European Planetary Science Congress , abstract no. 96; Englert P et al . 2014 In 45th Lunar and Planetary Science Conf. , abstract no. 1707). Feldspar, quartz and pyroxene are common minerals found in all the sediments. Minor abundances of carbonate, chlorite, actinolite and allophane are also found in the surface sediments, and are similar to minerals found in greater abundance in the lakebottom sediments. Surface sediment formation is dominated by physical processes; a few centimetres below the surface chemical alteration sets in, whereas lakebottom sediments experience biomineralization. Characterizing the mineralogical variations in these samples provides insights into the alteration processes occurring in the ADV and supports understanding alteration in the cold and dry environment on Mars.

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“…Raman spectroscopy is an extremely promising technique for life detection systems in space exploration. Therefore, the development of miniaturized instruments and their exploitation for the analysis of geological samples on Earth will prepare the possible future deployment of Raman instruments to test for pigments such as carotenoids deposited by extinct or extant organisms in the Mars regolith (9,34,35,62,63,(111)(112)(113)(114)(115)(116)(117)(118). Very recent publications review the state of the art of the use of portable and handheld Raman instruments and experience using these instruments (119)(120)(121).…”

Section: Advanced Raman Spectroscopic Techniques In Microbiologymentioning

confidence: 99%

Raman Spectroscopy of Microbial Pigments

Jehlička

Edwards

Oren

2014

Appl Environ Microbiol

148

114

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Raman spectroscopy is a rapid nondestructive technique providing spectroscopic and structural information on both organic and inorganic molecular compounds. Extensive applications for the method in the characterization of pigments have been found. Due to the high sensitivity of Raman spectroscopy for the detection of chlorophylls, carotenoids, scytonemin, and a range of other pigments found in the microbial world, it is an excellent technique to monitor the presence of such pigments, both in pure cultures and in environmental samples. Miniaturized portable handheld instruments are available; these instruments can be used to detect pigments in microbiological samples of different types and origins under field conditions.

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Optimizing the detection of carotene in cyanobacteria in a martian regolith analogue with a Raman spectrometer for the ExoMars mission

Cited by 77 publications

References 23 publications

2D Raman spectroscopy study of dolomite and cyanobacterial extracellular polymeric substances from Khor Al‐Adaid sabkha (Qatar)

2D Raman spectroscopy study of dolomite and cyanobacterial extracellular polymeric substances from Khor Al‐Adaid sabkha (Qatar)

Mineralogical analyses of surface sediments in the Antarctic Dry Valleys: coordinated analyses of Raman spectra, reflectance spectra and elemental abundances

Raman Spectroscopy of Microbial Pigments

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