title: Roles of ring-hydroxylating dioxygenases in styrene and benzene catabolism in Rhodococcus jostii RHA1.
abstract: Proteomics and targeted gene disruption were used to investigate the catabolism of benzene, styrene, biphenyl, and ethylbenzene in Rhodococcus jostii RHA1, a well-studied soil bacterium whose potent polychlorinated biphenyl (PCB)-transforming properties are partly due to the presence of the related Bph and Etb pathways. Of 151 identified proteins, 22 Bph/Etb proteins were among the most abundant in biphenyl-, ethylbenzene-, benzene-, and styrene-grown cells. Cells grown on biphenyl, ethylbenzene, or benzene contained both Bph and Etb enzymes and at least two sets of lower Bph pathway enzymes. By contrast, styrene-grown cells contained no Etb enzymes and only one set of lower Bph pathway enzymes. Gene disruption established that biphenyl dioxygenase (BPDO) was essential for growth of RHA1 on benzene or styrene but that ethylbenzene dioxygenase (EBDO) was not required for growth on any of the tested substrates. Moreover, whole-cell assays of the delta bphAa and etbAa1::cmrA etbAa2::aphII mutants demonstrated that while both dioxygenases preferentially transformed biphenyl, only BPDO transformed styrene. Deletion of pcaL of the beta-ketoadipate pathway disrupted growth on benzene but not other substrates. Thus, styrene and benzene are degraded via meta- and ortho-cleavage, respectively. Finally, catalases were more abundant during growth on nonpolar aromatic compounds than on aromatic acids. This suggests that the relaxed specificities of BPDO and EBDO that enable RHA1 to grow on a range of compounds come at the cost of increased uncoupling during the latter's initial transformation. The stress response may augment RHA1's ability to degrade PCBs and other pollutants that induce similar uncoupling.
authors.affiliation: Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.
authors.forename: Marianna A
authors.initials: MA
authors.lastname: Patrauchan
authors.forename: Christine
authors.initials: C
authors.lastname: Florizone
authors.forename: Shawn
authors.initials: S
authors.lastname: Eapen
authors.forename: Leticia
authors.initials: L
authors.lastname: Gómez-Gil
authors.forename: Bhanu
authors.initials: B
authors.lastname: Sethuraman
authors.forename: Masao
authors.initials: M
authors.lastname: Fukuda
authors.forename: Julian
authors.initials: J
authors.lastname: Davies
authors.forename: William W
authors.initials: WW
authors.lastname: Mohn
authors.forename: Lindsay D
authors.initials: LD
authors.lastname: Eltis
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D001554:Benzene / Q000378:metabolism*; D001555:Benzene Derivatives / Q000378:metabolism; D001713:Biphenyl Compounds / Q000378:metabolism; D017931:DNA Primers; D049308:Dioxygenases / Q000235:genetics / Q000378:metabolism*; D006900:Hydroxylation; D007700:Kinetics; D016133:Polymerase Chain Reaction; D020543:Proteome; D012240:Rhodococcus / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D020058:Styrene / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D001554:Benzene; D001555:Benzene Derivatives; D001713:Biphenyl Compounds; D017931:DNA Primers; D049308:Dioxygenases; D020543:Proteome; D020058:Styrene; C010574:biphenyl; C004912:ethylbenzene