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

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 pm-topographical effects (sample roughness), it was possible to display the abundance of high molecular weight (C(86)) 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 mu M2- to cm(2)-scale; and (iii) the more exact assignment of lipid biomarkers to their biological source.