2.3. Fatty alcohol quantificationFo

2.3. Fatty alcohol quantification
For total fatty alcohol quantification, a 100 μl cell culture was mixed with 200 μl acetone (containing 0.2 mM 1-heptanol as the internal standard). For cellular and extracellular quantification of fatty alcohols, cell cultures were first separated into cellular and media fractions by centrifugation. The cellular fraction was resuspended in 100 μl of water prior to mixing with 200 μl acetone, while the media fraction was directly mixed with 200 μl acetone. All samples were centrifuged and the supernatant transferred to GC vials. Metabolite analysis was performed with an Agilent 7890A gas chromatograph equipped with a 5975 mass spectrometry detector, as described previously (Akhtar et al., 2013). For 1-octanol and 1-hexanol identification, fragmentation patterns and retention times of the analytes were compared with the NIST mass spectral library and commercially available fatty alcohol standards. A standard curve for quantification was prepared with commercially sourced fatty alcohols. Data was normalised with respect to the internal standard and optical density at 600 nm. All given values are an average mean of measurements obtained from at least 6 independent cultures with error bars representing standard error.