Figure 4. Promoter insertion in front of disD gene.

(A) Three different types of expression constructs used for disorazol heterologous production. The first one is the original plasmid p15A-dis. The second one was modified via Red/ET recombineering by insertion of promoter P_cp25 in front of disD directly. The third one was deletion orf9 gene by P_cp25-spect^R so that P_cp25 was also upstream disD. (B) Quantification of heterologous disorazol production by HPLC-MS analysis of the culture extracts from different M. xanthus DK1622 mutant strains. Sections of extracted ion chromatograms at m/z = 745.45 corresponding to the [M + H]⁺ ion of disorazol A₂ are illustrated as representative readout of productivity. The M. xanthus DK1622 host strains contain one of the three expression constructs shown in (A).