Heterologously expressed β-hydroxyl fatty acids from a metagenomic library of a marine sponge

Functional screening based on the antibacterial activity of a metagenomic library of the Japanese marine sponge, Discodermia calyx, afforded three β-hydroxyl fatty acids: 3-hydroxypalmitic acid, 3-hydroxylauric acid and 3-hydroxymyristic acid, heterologously expressed in an antibacterial clone, pDC113. 3-Hydroxypalmitic acid showed moderate antibacterial activity against Bacillus cereus and Candida albicans. A sequence analysis of the insert DNA revealed 23 putative ORFs, with most sharing homology to bacterial fatty acid synthase II and lipid A biosynthesis enzymes. The other ORFs were probably transmembrane proteins involved in lipid A biosynthesis. Although lipid A was not detected under our experimental conditions, the production of β-hydroxyl fatty acids as components of lipid A were enhanced in pDC113.