Upper, flaviolin biosynthesis pathway: 5 molecules of malonyl-CoA are condensed by RppA to form flaviolin, which has a specific absorbance at 340 nm. Bottom, RppA was expressed with different MCS/ACC enzymes for characterization of malonyl-CoA availability in strain JC01 (DE3) ΔatoB. Engineered E. coli strains were cultured in LB-like MOPS medium + 2% (wt/v) glycerol. For strains harbouring MCS, 12 mM malonate sodium was also included. Error bars represent s.d. calculated from at least three biological replicates.