cis-11-Octadecenoic acid (cis-vaccenic acid) is an eighteen-carbon monounsaturated fatty acid that is a major fatty acid in bacteria, including intestinal bacteria, and usually a minor component in plant and animal tissues.1 However, some plants have a much higher concentration of cis-vaccenic acid than others.2 It is a positional isomer of oleic acid which is much more abundant in plants and animals. It is commonly used as a bacterial biomarker. Although lower growth temperatures generally cause microorganisms to produce more unsaturated fatty acids, a mutant Escherichia coli was found to overproduce cisvaccenic acid even at elevated temperatures.3
