CONCLUSION
Microbial biotechnology allows bacterial carotenoids to be used as alternatives to plant-based carotenoids because of the ease of genetic manipulation of prokaryotes compared with eukaryotes, such as yeasts, fungi, and plants. Here, we used SOE by PCR for gene reassembly to redirect carotenoid synthesis from the plant-pathogenic bacteriumPantoea ananatis . Using SOE by PCR, we reassembledcrtEB , crtEBI , andcrtEBIY for phytoene, lycopene, and β‑carotene production, respectively, using E. coli to express the reassembled operons. We found that carotenoids confer tolerance to the phytotoxin toxoflavin. The carotenoid production of P .ananatis is dependent on RpoS, which is regulated positively by Hfq/ArcZ and negatively by ClpP, similar to an important regulatory network of E . coli , HfqArcZ → RpoS Ͱ ClpXP. We also demonstrated that carotenoid production is regulated by Hfq-controlled QS, since the EanR negative regulator on RpoS must be expressed in the stationary phase.