RpoS dependent overexpression of carotenoids from Erwinia herbicola in OXYR deficient Escherichia coli

Carotenoid synthesis in Escherichia coli, when transformed with plasmid containing a carotenoid gene cluster from Erwinia herbicola (pPL376), is regulated by RpoS. When the plasmid was transformed into E. coli mutants that were oxyR minus, the intracellular carotenoid concentration dramatically increased from that observed in an oxyR plus allele. The higher carotenoid concentration in these mutants correlated with an increase in rpoS transcription as indicated by beta-galactosidase activity from a rpoS::lacZ promoter fusion. This indication of a higher concentration of carotenoids correlated with an increased resistance to hydrogen peroxide and near-ultraviolet radiation (310-400 nm; near-UV).