Aerobic synthesis of unsaturated fatty acids in a psychrotrophic bacterium, Pseudomonas sp. strain E-3, having two mechanisms for unsaturated fatty acid synthesis.

Abstract

3-Decynoyl N-acetylcysteamine (DNAC), a specific inhibitor of the anaerobic pathway for bacterial unsaturated fatty acid synthesis, completely inhibited the growth of a psychrotrophic bacterium, Pseudomonas sp. strain E-3 (Pseudomonas E-3), in a succinate-salt medium. But the DNAC-inhibited growth was effectively relieved by supplementing saturated fatty acid in the medium. Although the in vitro synthesis of unsaturated fatty acid was inhibited by DNAC, it became insensitive to DNAC when fatty acid synthase was assayed in the presence of the membrane fraction containing Δ9 fatty acyl-CoA desaturase.When Pseudomonas E-3 was grown on pentadecanoate, a fatty acid unnatural to this bacterium, the cells contained penta- and heptadecenoate in the phospholipid, and the content of these odd-numbered unsaturated fatty acids amounted to 57% of the total unsaturated fatty acids. By cleavage of the penta- and heptadecenoate with periodate/ permanganate, they were identified as Δ9 15:1 and Δ9 17:1, respectively. All this indicates that the aerobic fatty acid desaturase system evidently contributes to in vivo formation of at least a part of unsaturated fatty acids in this bacterium.