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| 2. |
- Odham, Goran, et al.
(author)
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Determination of microbial fatty acid profiles at femtomolar levels in human urine and the initial marine microfouling community by capillary gas chromatography-chemical ionization mass spectrometry with negative ion detection
- 1985
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In: Journal of Microbiological Methods. - : Elsevier BV. - 0167-7012. ; 3:5-6, s. 331-344
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Journal article (peer-reviewed)abstract
- Room temperature esterification with the electron capturing pentafluorobenzyl bromide in glass capillaries, with analysis by capillary gas-liquid chromatography coupled with chemical ionization mass spectrometry and negative ion detection in the selected ion mode, allowed detection and identification of fatty acids from microbial biofilms at the femtomolar level. This sensitivity was achieved without loss of specificity of the mass spectrometric analysis. The detection of all the fatty acids commonly associated with bacteria was quantitative and linearly related to their concentration at a sensitivity permitting detection of about 600 bacteria the size of Escherichia coli. With this technique it was possible to detect the characteristic 3-hydroxy fatty acid of the lipopolysaccharide lipid A of E. coli infecting human urine at concentrations representing 10 4 bacteria and define the community structure of the initial marine microfouling community attached to a teflon surface at concentrations below the detectability by gas chromatography with flame ionization detection.
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| 3. |
- Tunlid, Anders, et al.
(author)
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Determination of 13C-enrichment in bacterial fatty acids using chemical ionization mass spectrometry with negative ion detection
- 1987
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In: Journal of Microbiological Methods. - : Elsevier BV. - 0167-7012. ; 7:2-3, s. 77-89
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Journal article (peer-reviewed)abstract
- 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.
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| 4. |
- Tunlid, Anders, et al.
(author)
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Precision and sensitivity of the measurement of 15 N enrichment in D-alanine from bacterial cell walls using positive/negative ion mass spectrometry
- 1985
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In: Journal of Microbiological Methods. - 0167-7012. ; 3:3-4, s. 237-245
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Journal article (peer-reviewed)abstract
- Sensitive detection of cellular components from specific groups of microbes can be utilized as 'signatures' in the examination of microbial consortia from soils, sediments or biofilms. Utilizing capillary gas chromatography/mass spectrometry and stereospecific derivatizing agents, D-alanine, a component localized in the prokaryotic (bacteria) cell wall, can be detected reproducibly. Enrichments of D- 15 N]alanine determined in E. coli grown with [ 15 N]ammonia can be determined with precision at 1.0 atom%. Chemical ionization with methane gas and the detection of negative ions (M-HF) - · and (M-F or M+H - HF) - formed from the heptafluorobutyryl D-2 butanol ester of D-alanine allowed as little as 8 pg (90 fmol) to be detected reproducibly. This method can be utilized to define the metabolic activity in terms of 15 N incorporation at the level of 10 3 -10 4 cells, as a function of the 15 N- 14 N ratio.
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