MECHANISTIC ASPECTS OF THE PYROLYTIC METHYLATION AND TRANSESTERIFICATION OF BACTERIAL-CELL WALL LIPIDS

Coating a pyrolysis filament with whole bacterial cells, cell walls or lipid extracts followed by the addition of a suitable derivatizing agent (e.g. tetramethylammonium hydroxide or sodium metasilicate with alcohol) and subsequent pyrolysis, enables on-line derivatization and thermal extraction of volatile esters of the various fatty acid moieties present. It is shown that at least two competing reaction pathways appear to be involved, namely transesterification vs. hydrolysis (saponification) followed by methylation. In combination with a short capillary column gas-chromatographic separation and mass-spectrometric detection, the pyrolytic derivatization technique provides a rapid way for generating a chemotaxonomically characteristic profile of fatty acid methyl esters from a single bacterial colony.