Biosynthesis of (−)-α-bisabolol in engineered E. coli. a Schematic representation of (−)-α-bisabolol production in an engineered E. coli harboring endogenous 2-C-methyl-d-erythritol 4-phosphate (MEP) pathway genes and exogenous mevalonate (MVA) pathway genes. The native MEP pathway consists of: DXS deoxyxylulose 5-phosphate synthase; DXR deoxyxylulose 5-phosphate reductoisomerase; CMS 2-C-methylerythritol 4-phosphate cytidyl transferase; CMK 4-(cytidine 5′-diphospho)-2-C-methylerythritol kinase; MDS 2-C-methylerythritol 2,4-cyclodiphosphate synthase; HDS (E)-4-hydroxy-3-methylbut-2-enyl diphosphate reductase; and HDR hydroxymethylbutenyl diphosphate reductase. The engineered mevalonate pathway consists of seven enzymes: MvaE, acetoacetyl-CoA thiolase (GenBank accession number: AF290092); MvaS, 3-hydroxy-3-methylglutaryl- CoA synthase (GenBank accession number: AF290092); MvaA, 3-hydroxy-3-methylglutaryl-CoA reductase (GenBank accession number: AF290092); MvaK1, mevalonate kinase (GenBank accession number: AF290099); MvaK2, phosphomevalonate kinase (GenBank accession number: AF290099); MvaD, mevalonate 5-diphosphate decarboxylase (GenBank accession number: AF290099); Idi, isopentenyl diphosphate isomerase (GenBank accession number: AF119715); and IspA, geranyl diphosphate synthase or farnesyl diphosphate synthase (GenBank accession number: AAC73524). MrBBS; E. coli codon-optimized (−)-α-bisabolol synthase of German chamomile (GenBank accession number: KU680479). b Plasmid constructs used for (−)-α-bisabolol production in E. coli. pTSN-MrBBS, pTrc99A with MrBBS gene from German chamomile; pSSN12Didi, pSTV28 containing mvaK1, mvaD, mvaK2 of Streptococcus pneumoniae, and idi of Escherichia coli; pSNA-MrBBS, pSTV28 containing mvaK1, mvaK2, and mvaD of S. pneumoniae, idi of E. coli, mvaE and mvaS of Enterococcus faecalis, and MrBBS of German chamomile; pSNA-MrBBS-IspA, pSNA-MrBBS containing ispA of E. coli