Measurement of phospholipid fatty acids at picomolar concentrations in biofilms and deep subsurface sediments using gas chromatography and chemical ionization mass spectrometry
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Examination of ester-linked phospholipid fatty acids (PLFA) have provided a means to characterize the community structure of microbial assemblies. Attempts to analyze such acids at low picomolar levels in environmental samples by gas chromatography and chemical ionization mass spectrometry (CIMS) using positive or negative ion detection, showed that the limit of detection (LOD) was mainly dependent on the background levels of fatty acids, introduced as contaminants during the preparation of the samples. The lowest backgrounds were obtained using a procedure preparing methyl esters of fatty acids by a mild alkaline transesterification, followed by analysis with positive ion CIMS. The blank samples of this procedure were three times as low as and less variable than the background values obtained using a procedure involving preparation of pentafluorobenzyl (PFB)-esters for negative ion CIMS. The LOD (background values + three times the standard deviation) of the positive ion CIMS method was approximately 30 pmole. The coefficient of variation (n = 5) for determining the proportions and amounts of PLFA in microgram amounts of Escherichia coli cells using the developed CIMS method were between 2-30%, depending of the amount of extracted cells and the fatty acids analyzed. The recovery of the PLFA was between 63% and 100%. The positive ion CIMS method was used to determine PLFA in deep subsurface samples with a LOD of approximately 2-3 pmoles/g dry wt corresponding to a fatty acid content of 105-106 bacterial cells/g dry wt. Measurement of PLFA in Pseudomonas atlantica grown in a Fowler cell adhesion module demonstrated differences in membrane composition between free and attached cells in biofilms.
Ämnesklassifikation (UKÄ) – OBLIGATORISK
|Tidskrift||Journal of Microbiological Methods|
|Status||Published - 1989 jan 1|
|Peer review utförd||Ja|