Degradation of chloroaromatics by Pseudomonas putida GJ31: assembled route for chlorobenzene degradation encoded by clusters on plasmid pKW1 and the chromosome

Abstract

Pseudomonas putida GJ31 has been reported to grow on chlorobenzene using a meta-cleavage pathway with chlorocatechol 2,3-dioxygenase (CbzE) as a key enzyme. The CbzE-encoding gene was found to be localized on the 180 kb plasmid pKW1 in a cbzTEXGS cluster, which is flanked by transposases and encodes only a partial (chloro)catechol meta-cleavage pathway comprising ferredoxin reductase, chlorocatechol 2,3-dioxygenase, an unknown protein, 2-hydroxymuconic semialdehyde dehydrogenase and glutathione S-transferase. Downstream of cbzTEXGS are located cbzJ, encoding a novel type of 2-hydroxypent-2,4-dienoate hydratase, and a transposon region highly similar to Tn5501. Upstream of cbzTEXGS, traNEOFG transfer genes were found. The search for gene clusters possibly completing the (chloro)catechol metabolic pathway of GJ31 revealed the presence of two additional catabolic gene clusters on pKW1. The mhpRBCDFETP cluster encodes enzymes for the dissimilation of 2,3-dihydroxyphenylpropionate in a novel arrangement characterized by the absence of a gene encoding 3-(3-hydroxyphenyl)propionate monooxygenase and the presence of a GntR-type regulator, whereas the nahINLOMKJ cluster encodes part of the naphthalene metabolic pathway. Transcription studies supported their possible involvement in chlorobenzene degradation. The upper pathway cluster, comprising genes encoding a chlorobenzene dioxygenase and a chlorobenzene dihydrodiol dehydrogenase, was localized on the chromosome. A high level of transcription in response to chlorobenzene revealed it to be crucial for chlorobenzene degradation. The chlorobenzene degradation pathway in strain GJ31 is thus a mosaic encoded by four gene clusters.

Isolation and Functional Gene Analyses of Aromatic-Hydrocarbon-Degrading Bacteria from a Polychlorinated-Dioxin-Dechlorinating Process

“…This arrangement of catabolic genes is similar to those found in AHD bacteria containing AhDO of the class IIB dioxygenase family (see Fig. 3), such as Pseusomonas putida strain GJ31 (29) and Rhodococcus globerulus strain P6 (2). …”

New Hydrocarbon Degradation Pathways in the Microbial Metagenome from Brazilian Petroleum Reservoirs

“…We found that the metagenomic fragments contained subsets of genes belonging to different pathways previously described in other assemblages for anaerobic and aerobic degradation of different aromatic and aliphatic compounds (Figure 5). The degradation of environmental aromatic compounds through the concerted action of various fragmented pathways has been previously observed using metagenomic data [41], [42] and in isolated strains [43].…”

Bacterial degradation of chlorophenols and their derivatives

“…In the second case, bacteria may utilize 3CC completely. This type of pathway has been observed in the degradation of chloro-aromatics by Pseudomonas putida GJ31 [43]. In strain GJ31, 3CC was cleaved into 2-hydroxy- cis - cis -muconate by a catechol-2,3-dioxygenase that was further degraded completely [43] [Figure 3c].…”

“…In the meta -cleavage pathway, there are two possibilities for 3CC degradation: (i) formation of a dead end product [39,42] and (ii) complete mineralization of 3CC [43]. In the first case, a suicide compound, 5-chloroformyl-2-hydroxypenta-2,4-dienoic acid, is formed due to the meta -cleavage of 3CC, which inactivates catechol-2,3-dioxygenase (EC = 1.13.11.2), resulting in 3CC accumulation in the media.…”