Fig. 1

Production of bacterial indigoidine in engineered S. cerevisiae. a S. cerevisiae exhibits two distinct metabolic states which are accompanied with distinct metabolic flux profiles. The width of the arrows represents metabolic flux. Blue arrows represent purely respiratory state, while red arrows represent fully fermentative state. GAP glyceraldehyde 3-phosphate, DHAP dihydroxyacetone phosphate, EtOH ethanol, α-KG α-ketoglutarate, Glu glutamate, Gln glutamine. Several known pathways for glutamine biosynthesis are shown. The depiction of metabolite intermediates and their cellular localization adapted from Frick et al. Ljungdahl and Daignan-Fornier, and Chen et al. [10, 48, 49]. b Activation of the apo-form of the S. lavendulae NRPS, BpsA (blue pigment synthetase A) by the Bacillus subtilis 4′-phosphopantetheinyl transferase (PPTase; Sfp) via addition of a coenzyme A-derived moiety to the peptide carrier domain (PCP) into the active holo-form. The active holo-BpsA converts two l-glutamines to one molecule of the blue pigment indigoidine by a catalytic process involving adenylation (a), oxidation (Ox) and thioesterase (TE) domains. c Positive S. cerevisiae transformants exhibit blue pigmentation occurring 3 days after visible colony formation on solid media containing glucose. d Brightfield microscopy of the pigmented colony shows heterogeneity in pigment production, ×63 zoom. The pigment shows punctate subcellular localization, scale bar = 10 µm, increasing non-linear magnification of boxed areas is depicted by pull-outs