Analysis of archaeal core ether lipids using Time of Flight–Secondary Ion Mass Spectrometry (ToF-SIMS): Exploring a new prospect for the study of biomarkers in geobiology

Authors


Corresponding author: V. Thiel. Tel.: +49 +551 3914395; fax: +49 +551 397918; e-mail: vthiel@gwdg.de.

ABSTRACT

The capability of Time of Flight–Secondary Ion Mass Spectrometry (ToF-SIMS) of analysing molecular archaeal biomarkers in geobiological samples was tested and demonstrated. Using a bismuth cluster primary ion source, isopranyl glycerol di- and tetraether core lipids were detected in small amounts of total organic extracts from methanotrophic microbial mats, simultaneously and without further chemical treatment and chromatographic separation. ToF-SIMS was also employed to track the distribution of fossilized ether lipids in a massive carbonate (aragonite) microbialite that precipitated as a result of the microbial anaerobic oxidation of methane. An unambiguous signal was obtained when analysing a freshly broken rock surface (base of a microdrill core). Though some limitation occurred due to µm-topographical effects (sample roughness), it was possible to display the abundance of high molecular weight (C86) of tetraethers exposed in particular regions of the rock surface. ‘Molecular mapping’ revealed that a part of these molecules was encased within the rock fabric in a cluster-like distribution that might trace the arrangement of the calcifying microbial colonies in the once active mat system. The results reveal promising perspectives of ToF-SIMS for (i) the quasi-nondestructive analysis of lipids in extremely small geobiological samples at low concentrations; (ii) resolving the spatial distribution of these compounds on a µm2- to cm2-scale; and (iii) the more exact assignment of lipid biomarkers to their biological source.

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