Isolation and biosynthesis of an unsaturated fatty acid with unusual methylation pattern from a coral-associated bacterium Microbulbifer sp.

(2Z,4E)-3-Methyl-2,4-decadienoic acid (1) was identified as a major metabolite from a culture extract of a marine bacterium Microbulbifer which was collected from a stony coral Porites sp. NMR-based spectroscopic analysis revealed that 1 is an unsaturated fatty acid in which a methyl group is located in an uncommon position as a natural product. Feeding experiments of C-13-labeled precursors clarified that L-methionine-derived methylation takes place at the carbon which is derived from the carbonyl carbon of acetate. Compound 1 showed weak growth inhibition against Saccharomyces cerevisiae.