Fig. 2

a Scheme of expression plasmids used in this study for synthesis of roseoflavin. The genes encoding enzymes for synthesis of roseoflavin (rosB, rosA), the gene RFK encoding a human riboflavin kinase and ribM encoding a flavin transporter were arranged as synthetic operons and coupled to different expression plasmids. The resulting vector constructs were introduced into selected bacterial hosts to create the recombinant strains RML1–7. Codon-optimized genes for expression in Bacillus subtilis were used in pRML1–4, whereas wild-type genes from Streptomyces davaonensis (rosB* and rosA*) were used in pSETPermErosArosB. P promoter, T terminator; yellow boxes, ribosomal binding sites. Features are not scaled to their original size. b PCR analysis of the recombinant bacterial strains used in this study. Amplicons of predicted size (shown by arrows) were produced for each sample using specific primers (for details see Table 2) binding to sequences up- and downstream from the genes to be expressed (RML1–7) or to empty cloning sites (C1–7). Either plasmid DNA (from strains C1, RML1, C3, RML3, C5–6, RML5 and RML6) or genomic/chromosomal DNA samples (from strains C2, RML2, C4, RML4, C7 and RML7) were used as DNA templates