Fig. 1

Network investigated in this work. The metabolic map shows the steps involved in the biochemical conversion of glucose to isoprenoids. Isoprenoid biosynthesis can occur via the two orthogonal 2-C-methyl-d-erythritol 4-phosphate (MEP, blue arrows) and mevalonate (MVA, orange arrows) pathways. For the MEP pathway, the 1-deoxy-d-xylulose 5-phosphate reductoisomerase (dxr) gene is shown. This gene is targeted for inactivating the endogenous isoprenoid pathway. Both modules branch from the central metabolism and converge to isopentenyl-diphosphate (IPP) and dimethylallyl-diphosphate (DMAPP), which are the precursors of all isoprenoids. Moreover, the biosynthetic pathway of the storage compound poly-β-hydroxybutyrate (PHB) is included (box with red outline). This consists of two enzymatic reactions encoded by the genes phaB and phaC1 and phaC2 (both in green). The network includes also the schematic representation of the Krebs cycle, which includes conversion of 2-oxoglutarate (2-OXO) to succinyl-CoA. Eventually, accumulation of PYR or 2-OXO can result in their secretion in the medium (boxes with yellow and light-blue outline, respectively). Additionally, conversion of (R)-3hydroxybturyryl-CoA ((R)-3HB-CoA) to (R)-3HB can result in the secretion of the latter compound (box with purple outline). Other abbreviations: reduced flavodoxin (Fld), ferredoxin (Fd), red: reduced, ox: oxidized. GAP (glyceraldehyde-3-phosphate), PYR (pyruvate), CDP-ME (4-(cytidine 5′-diphospho)-2-C-methyl-d-erythritol), CDP-MEP (2-phospho-4-(cytidine 5′-diphospho)-2-C-methyl-d-erythritol), MEcPP (2-C-methyl-d-erythritol 2,4-cyclodiphosphate), Ac-CoA (acetyl-CoA), AA-CoA (acetoacetyl-CoA), HMG-CoA (S)-3-hydroxy-3-methylglutaryl-CoA), MVA-P ((R)-5-phosphomevalonate), MVA-PP ((R)-5-diphosphomevalonate)