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Anaerobic Activation of p-Cymene in Denitrifying Betaproteobacteria: Methyl Group Hydroxylation versus Addition to Fumarate

Lookup NU author(s): Marta Drozdowska, Emeritus Professor Bernard Golding

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Abstract

The betaproteobacteria "Aromatoleum aromaticum" pCyN1 and " Thauera" sp. strain pCyN2 anaerobically degrade the plant-derived aromatic hydrocarbon p-cymene (4-isopropyltoluene) under nitrate-reducing conditions. Metabolite analysis of p-cymene-adapted " A. aromaticum" pCyN1 cells demonstrated the specific formation of 4-isopropylbenzyl alcohol and 4-isopropylbenzaldehyde, whereas with "Thauera" sp. pCyN2, exclusively 4-isopropylbenzylsuccinate and tentatively identified (4-isopropylphenyl) itaconate were observed. 4-Isopropylbenzoate in contrast was detected with both strains. Proteogenomic investigation of p-cymene-versus succinate-adapted cells of the two strains revealed distinct protein profiles agreeing with the different metabolites formed from p-cymene. " A. aromaticum" pCyN1 specifically produced (i) a putative p-cymene dehydrogenase (CmdABC) expected to hydroxylate the benzylic methyl group of p-cymene, (ii) two dehydrogenases putatively oxidizing 4-isopropylbenzyl alcohol (Iod) and 4-isopropylbenzaldehyde (Iad), and (iii) the putative 4-isopropylbenzoate-coenzyme A (CoA) ligase (Ibl). The p-cymene-specific protein profile of "Thauera" sp. pCyN2, on the other hand, encompassed proteins homologous to subunits of toluene-activating benzylsuccinate synthase (termed [4-isopropylbenzyl] succinate synthase IbsABCDEF; identified subunits, IbsAE) and protein homologs of the benzylsuccinate beta-oxidation (Bbs) pathway (termed BisABCDEFGH; all identified except for BisEF). This study reveals that two related denitrifying bacteria employ fundamentally different peripheral degradation routes for one and the same substrate, p-cymene, with the two pathways apparently converging at the level of 4-isopropylbenzoyl-CoA.

Publication metadata

Author(s): Strijkstra A, Trautwein K, Jarling R, Wohlbrand L, Dorries M, Reinhardt R, Drozdowska M, Golding BT, Wilkes H, Rabus R

Publication type: Article

Publication status: Published

Journal: Applied and Environmental Microbiology

Year: 2014

Volume: 80

Issue: 24

Pages: 7592-7603

Print publication date: 01/12/2014

Online publication date: 26/09/2014

Acceptance date: 23/09/2014

Date deposited: 24/10/2016

ISSN (print): 0099-2240

ISSN (electronic): 1098-5336

Publisher: American Society for Microbiology

URL: http://dx.doi.org/10.1128/AEM.02385-14

DOI: 10.1128/AEM.02385-14

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