Fig. 4.

Expression of the Δ5-Des gene in S. meliloti 1021FDC5 leads to formation of Δ5-unsaturated free fatty acids. Partial gas chromatograms of methyl esters obtained from fatty acids in the spent culture medium of 1021FCD5 carrying an empty vector (A) or expressing the Δ5-Des gene (B) are shown. The different fatty acids in panel A were confirmed by comigration and by comparison of their mass spectra with authentic standards. The Δ5-modified fatty acids were identified by comparison with reported spectra (see Fig. S1 and S2 in the supplemental material).