Modes of Fatty-Acid Desaturation in Cyanobacteria

Abstract

The mode of desaturation of fatty acids in the membrane lipids of cyanobacteria was studied by analyzing the composition of fatty acids, the distribution of fatty acids at the sn position of the glycerol moiety, and the position of double bonds in the fatty acids. Cyanobacterial strains can be classified into four groups on the basis of the mode of desaturation of fatty acids. Cyanobacteria in Group 1 can introduce only one double bond at the Δ9 position of fatty acids at the sn-1 position. Cyanobacteria in Groups 2, 3 and 4 are characterized by a unique positional distribution of fatty acids; the C18 and C16 fatty acids are esterified, respectively, to the sn-1 and sn-2 positions of the glycerol moiety. In Group 2, the C18 acid is desaturated at the Δ9, Δ12, and Δ15 positions and the C16 acid is desaturated at the Δ9 and Δ12 positions; in Group 3, the C18 acid is desaturated at the Δ6, Δ9, and Δ12 positions; and in Group 4, the C18 acid is desaturated at the Δ6, Δ9, Δ12, and Δ15 positions. The C16 acid is not desaturated in Groups 3 and 4. Both unicellular and filamentous strains are distributed among all four groups.