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 reassembledcrtE –B , crtE –B –I , andcrtE –B –I –Y 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.