MOESM3 of Enhancing surfactin production by using systematic CRISPRi repression to screen amino acid biosynthesis genes in Bacillus subtilis

Additional file 3: Figure S1. Construction of the surfactin production B. subtilis strain BS168NU-S. (A) Schematic diagram of the double crossover homologous recombination for construction of the recombinant B. subtilis strain BS168NU-S. Phosphopantetheinyl transferase (PPTase), which plays an essential role in surfactin synthesis, is encoded by the sfp gene. However, sfp in the wild-type B. subtilis 168 strain (BS168NU) is inactive due to a termination codon in the middle of the gene sequence. We thus integrated the sfp gene under the control of the P43 promoter into the ydeO site of the BS168NU genome using double crossover homologous recombination and the Spizizen transformation approach. (B) Surfactin production by the B. subtilis strains of BS168NU and BS168NU-S 24 h after inoculation in 5 mL of semi-defined fermentation medium without xylose inducer