Determination of 13C-enrichment in bacterial fatty acids using chemical ionization mass spectrometry with negative ion detection
Saturated, monoenoic and β-hydroxysubstituted fatty acids, 13C-labelled at the carboxyl group, were prepared from natural or synthetic unlabelled analogues. The synthetic route involves decarboxylation of the unlabelled fatty acid to the next lower iodide, displacement of iodide for [13C]cyanide and hydrolysis. The fatty acids were converted to their pentafluorobenzyl esters and analysed by selected ion monitorint using chemical ionization and negative ion detection. Measurements of the signal ratios for the negative carboxylate ion (m) and the (m + 1) ion showed that at 95% confidence level and n = 5, mean values differing by 1.0 atom% 13C will be significantly resolved. The calculated standard deviation was the same for the studied bacterial acids including the phospholipid ester-linked palmitoleic acid, β-hydroxymyristic acid in the lipopolysaccharides and β-hydroxybutyric acid in the storage polymer poly-β-hydroxyalkanoate. Sodium [1-13C]acetate or D-[13C6]glucose were pulse administered to a Gram-negative marine bacterium isolate. Phospholipid ester-linked fatty acids and β-hydroxybutyric acid showed extensive 13C-incorporation within 15 min after the pulse. After approximately 60 min a maximum of 10 atom% excess of 13C was reached for palmitoleic acid. The method provides the potential to measure the metabolic activity of bacterial communities by measuring the incorporation of 13C-labelled substrates into specific fatty acids that can be utilized as biomarkers for biomass, community structure and nutritional status.
- Bacterial acids
- Negative ion chemical ionization
- Phospholipid ester-linked fatty acids
- Selected ion monitoring
- Stable isotope labelling
- ISSN: 0167-7012
- MICCS, Molecular Interactions Controlling Soil Carbon Sequestration
- Mobilization of organic nitrogen by ectomycorrhizal fungi
- Diversity of litter decomposition strategies in mushroom forming fungi
- Cellulose decomposition mechanisms of mushroom forming fungi
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Capture of the nematode Panagrellus redivivus by the soil-living fungus Arthrobotrys oligospora.