Lycopene elongases and C50 cyclases function in the natural C40-to-C50 pathway. HPLC chromatograms of carotenoid extracts from E. coli cells harboring plasmids with genome-derived natural gene cluster (a) or RBS-redesigned artificial operons (b), together with lycopene biosynthetic genes. Peak numbers correspond with those indicated in c and Fig. 1. (c) Absorbance spectra of indicated compounds.