The styrene-catabolic system of P. fluorescens ST. (A) Organization of the stySR regulatory and of the styABCDE catabolic operons in Pseudomonas spp. styS, sensor histidine kinase; styR, response regulator; styA and styB, styrene monooxygenase (SMO); styC, styrene oxide isomerase (SOI); styD, phenylacetaldehyde dehydrogenase (PADH); styE, styrene transport protein. PstyS and PstyA are the promoters of the regulatory and catabolic operons, respectively. (B) Schematic representation of the PstyA promoter region. Inverted red arrows, StyR-P-binding sites STY1, STY2 and STY3 (numbering refers to distance from PstyA transcription start site). Blue box, IHF-binding site. Bent arrow, transcription start site.