Genes involved in the anaerobic degradation of toluene in a denitrifying bacterium, strain EbN1

Abstract

The organization of all genes required for the anaerobic conversion of toluene to benzoyl-CoA was investigated in denitrifying Azoarcus-like strain EbN1. All of these genes are clustered within 25.3 kb of contiguous DNA sequence, which includes only a few intervening sequences. The toluene-catabolic genes are organized in two apparent operons. One contains the genes ( bssCAB) for the three subunits of benzylsuccinate synthase, which initiates anaerobic toluene degradation by converting toluene to ( R)-benzylsuccinate. The BssCAB proteins of strain EbN1 are most similar to those of Thauera aromatica strain K172. The bssCAB genes are part of a larger putative operon ( bssDCABEFGH), which contains the gene bssD, encoding the activase for benzylsuccinate synthase, and four genes ( bssEFGH) encoding proteins of unknown function. RT-PCR experiments showing continuation of transcription over the three largest intergenic regions of the bss operon support the assumed structure. Moreover, BssG was identified as toluene-induced protein. Downstream of the bss genes, another large putative operon ( bbsA- H) was identified that contains all genes required for beta-oxidation of benzylsuccinate to benzoyl-CoA, e.g. bbsEF, encoding succinyl-CoA:( R)-benzylsuccinate CoA-transferase. Immediately upstream of the bss operon, genes for a two-component regulatory system were identified; their products may sense toluene and induce the expression of both catabolic operons. The order and sequences of the bss and bbs genes are highly similar among toluene-degrading denitrifiers. The bss and bbs genes of the Fe(III)-reducing Geobacter metallireducens display less sequence similarity and are organized differently. The genes between the bss and bbs operons and in the flanking regions differ between strain EbN1 and the other strains.

Genetic and chemical characterization of ibuprofen degradation by Sphingomonas Ibu-2

“…5) (Kube et al, 2004;Kühner et al, 2005;Leuthner & Heider, 2000). Our genetic and sequence data suggest that IpfD, a putative thiolase, may partner with IpfE, a protein which contains a DUF35 domain, just as the thiolase BbsB partners with the DUF35 protein BbsA.…”

“…2) we hypothesize that IpfD and E are responsible for the acid side chain removal based on the role that related proteins play in acyl group transfer (Fig. 4) (Bangera & Thomashow, 1999;Kube et al, 2004;Kühner et al, 2005;Leuthner & Heider, 2000;Verhoeven & Jakobs, 2001;Wanders et al, 1997;Westin et al, 2007).…”

“…W. Murdoch and A. G. Hay Although there are over 2000 SCPx-type bacterial genes in the NCBI database, only four have been characterized to any degree: ditF (Pseudomonas abietaniphila), phlC (P. putida) (Bangera & Thomashow, 1999), ORF-2 from the camphor catabolic cluster (Rhodococcus sp. NCIMB 9784) (Grogan et al, 2001;Roberts et al, 2004), and bbsB from both Aromatoleum aromaticum EbN1 (Kube et al, 2004;Kühner et al, 2005) and Thauera aromatica (Leuthner & Heider, 2000). As part of a pathway for the metabolism of toluene to benzoyl-CoA under anaerobic denitrifying conditions, BbsB in conjunction with BbsA performs the decondensation of an a-aliphatic b-keto CoA adduct in a manner that mirrors the role of eukaryotic SCPx in the metabolism of bile acids and branched fatty acids (Fig.…”

“…Cooperation between an SCPx thiolase and a DUF35 protein has also been reported for PhlB and PhlC, which are involved in acetylation of an aromatic polyketide in P. putida (Bangera & Thomashow, 1999). (Kube et al, 2004;Kü hner et al, 2005) and Thauera aromatica (Leuthner & Heider, 2000).…”

Anaerobic Catabolism of Aromatic Compounds: a Genetic and Genomic View

“…The bssF gene was predicted to be part of the bss operon because genes coding for highly similar proteins are found directly downstream of bssE in all completely sequenced bss clusters (Fig. 16), although the function of BssF in toluene degradation is still unknown (202). However, in Azoarcus sp.…”