Fig. 1

Overview of the pathway engineering strategy for succinate production in S. elongatus PCC 11801. a An abridged central carbon pathway with the overexpressed genes shown in green font and genes that are knocked out in orange font with a cross on the reaction arrow. Blue lines represent the native pathway of PCC 11801. Different subsets of genetic modifications were incorporated in strains SA1–SA8 while all the modifications are present in SA9. Strain details in Table 1 and Additional file 1: Table S1. Results of metabolomics studies for the strain SA7 are superimposed on the pathway by color coding the metabolites. The metabolites depicted in purple show depletion while the ones in red show accumulation in S. elongatus PCC 11801 SA7 compared to the wild-type. b Schematic for homologous recombination of the three gene construct into the NSI site of S. elongatus PCC 11801 chromosome. The locus tag are: OgdA-Synpcc7002_A2770, SsaD-P25526, and PEPC-Synpcc7942_2252. c Schematic showing homologous recombination of a construct of Synpcc7942_0612 (gltA), Synpcc7942_0505 (SBPase) at the glgA site. d Schematic showing homologous recombination of E. coli succinate transporter genes, POADD2 (yjjP) and POADD5 (yjjB) at the sdhB site of PCC 11801. Enzymes: PEPC, PEP carboxylase; GltA, citrate synthase; OgdA, 2-ketoglutarate decarboxylase; SsaD, NADP-dependent succinate semialdehyde dehydrogenase, sdhB, Succinate dehydrogenase subunit B; SBPase/FBPase, fructose-1,6-biphosphatase/sedoheptulose-1,7-biphosphatase; glgA, glycogen synthase; metabolites: Glg, glycogen; ADPG, adenosine-5′-diphosphoglucose; G1P, glucose 1-phosphate; G6P, glucose 6-phosphate; F6P, fructose 6-phosphate; FBP, fructose bisphosphatase; G3P, glyceraldehyde 3-phosphate; 3PGA, 3-phosphoglyceric acid; PEP, phosphoenolpyruvate; Pyr, pyruvate; AcCoA, acetyl CoA; Cit, citrate; ICI, isocitrate; α-KG, alpha ketoglutarate; SuccCoA, succinyl CoA; Fum, fumarate; Mal, malate; OAA, oxaloacetate; RuBP, ribulose 1,5-bisphosphate; Ru5P, ribose 5-phosphate; S7P, sedoheptulose 7-phosphate; SBP, sedoheptulose 1,7-bisphosphate; GOX, glycolate oxidase; GLY, glycine; GLU, glutamate; 6PG, 6-phosphogluconate; Suc, sucrose; Suc6P, sucrose 6-phosphate; Glc6P, glucose-6-phosphate; GlcPNAc, N-acetylglucosamine; UDP-MurNAc, UDP-N-acetylmuramic acid. Additional details of the metabolites in Additional file 1: Table S6