Figure 4.

Identification of key genes of the SA pathway involved in the biosynthesis of aromatic byproducts QA and DHS from SA as determined by global transcriptomic analysis in E. coli W3110.shik1. Overexpression of ydiB, aroD, and ydiN genes allowed proposing that under carbon limiting growth conditions, SA is intracellularly accumulated as consequence of an inefficient export to periplasmic space or as consequence of its back transport to the cytoplasm as consequence of extracellular accumulation. YdiN, a putative transporter coded by ydiN was proposed to be involved in SA back import. Backflow of SA to DHS was possibly catalyzed by YdiB, whereas synthesis of DHQ from DHS was performed by AroD enzyme and finally, YdiB performed synthesis of QA from DHQ. Adapted from Johansson and Lidén (2006).