Location of double bonds in monounsaturated fatty acids of Campylobacter cryaerophila with dimethyl disulfide derivatives and combined gas chromatography-mass spectrometry.

Location of the double-bond position of monounsaturated fatty acids in Campylobacter cryaerophila was accomplished with combined gas chromatography-mass spectrometry analysis of dimethyl disulfide (DMDS) derivatives. The monoenoic fatty acids from whole bacterial cells were converted to methyl esters and then to DMDS adducts and analyzed by capillary gas chromatography-mass spectrometry. The mass spectra of DMDS adducts gave an easily recognizable molecular ion (M+) and two major diagnostic ions attributable to fragmentation between the two CH3S groups located at the original site of unsaturation. Two previously unidentified acids that distinguish C. cryaerophila from other bacteria were identified as C14:1 omega 7 and C16:1 omega 7 from their mass spectral fragmentation patterns. Resolution of cis and trans isomers by capillary column gas chromatography permitted assignment of the trans isomer to the C16:1 omega 7 acid.