Fig. 9.

Incorporation of octanoic-d₁₅ acid into membrane fatty acids of wild type (panel A) versus ΔfabH bypass mutant (panel B) L. lactis strains. Cultures were grown overnight in GM17 medium supplemented with 100 μM octanoic-d₁₅ acid. Phospholipids were extracted and analyzed via mass spectrometry as described in Materials and Methods. Note that the masses of the C19 CFA lacking isotopic enrichment and cis-vaccenic acid-d₁₅ acid are very similar (295.3 and 296.3, respectively) and thus identification of the peak in this region in the bypass mutant phospholipids is problematical. However, labeling with radioactive octanoate showed incorporation of octanoic acid into cis-vaccenic acid (data not shown).