Authors: Petr Vítek Carmen Ascaso Octavio Artieda Jacek Wierzchos
Publish Date: 2016/04/07
Volume: 408, Issue: 15, Pages: 4083-4092
Abstract
The Raman imaging method was successfully applied for mapping the distribution of biomolecules eg pigments associated with cryptoendolithic and hypoendolithic microorganisms as well as the inorganic host mineral matrix that forms the habitat for the biota To the best of our knowledge this is the first comprehensive study in the field of geomicrobiology based on this technique The studied microbial ecosystem was located nearly 3000 m above sea level within the driest desert on Earth the Atacama in Chile Enhancement of carotenoid Raman signal intensity close to the surface was registered at different areas of endolithic colonization dominated by algae with cyanobacteria present as well This is interpreted as an adaptation mechanism to the excessive solar irradiation On the other hand cyanobacteria synthesize scytonemin as a passive UVscreening pigment found at both the hypoendolithic and cryptoendolithic positions The distribution of the scytonemin Raman signal was mapped simultaneously with the surrounding mineral matrix Thus mapping was done of the phototrophic microorganisms in their original microhabitat together with the host rock environment Important information which was resolved from the Raman imaging dataset of the host rock is about the hydration state of Casulfate demonstrated on the presence of gypsum CaSO4·2H2O and the absence of both anhydrite CaSO4 and bassanite CaSO4·1/2H2O Obtaining combined “in situ” simultaneous information from the geological matrix inorganic together with the microbial biomolecules organic is discussed and concluded as an important advantage of this technique We discuss how selection of the laser wavelength 785 and 5145nm influences the Raman imaging results
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