Determination of double bond configuration of 2-hydroxy-fatty acids and emendation of cellular fatty acid composition of Aureispira marina and Aureispira maritima

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Aureispira marina is a marine bacterium with gliding motility isolated from the southern coastline of Thailand. It contained ceramide as a major cellular lipid composed of saturated or unsaturated branched chain 2-hydroxy-fatty acid and sphingosine. The structure of unsaturated 2-hydroxy-fatty acid was investigated in our previous study, but the geometric configuration of the double bond remained unclear. In the present study, 14-methyl-∆²-pentadecenol (∆²-iso-C_16:1-ol) was prepared from D-2-hydroxy-15-methyl-∆³-hexadecenoic acid (D-2-OH-∆³-iso-C_17:1) of the ceramide component, and analyzed by ¹H and ¹³C NMR in comparison with ∆²-trans-hexadecenol (∆²-trans-n-C_16:1-ol) derived from commercially available D-sphingosine. From the coupling constants of protons in the double bond and the chemical shift value of allylic carbon, the configuration of the double bond was determined as trans. Since the structure of 2-hydroxy-fatty acids was clarified, cellular fatty acids of A. marina and A. maritima, another species of the genus Aureispira, were reexamined, and the description on the cellular fatty acid composition of the genus Aureispira in the previous papers (Hosoya et al., 2006, Int. J. System. Evol. Microbiol., 56, 2931-2935; Hosoya et al., 2007, Int. J. System. Evol. Microbiol., 57, 1948-1951) lacking the description of 2-hydroxy-fatty acids was emended.