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Microorganisms degrading chlorobenzene via a meta-cleavage pathway harbor highly similar chlorocatechol 2,3-dioxygenase-encoding gene clusters. Arch Microbiol 182: 147-156

Chemische Mikrobiologie, Bergische Universität Wuppertal, Fachbereich C, Gaubetastrabetae 20, 42097 Wuppertal, Germany.
Archives of Microbiology (Impact Factor: 1.67). 11/2004; 182(2-3):147-56. DOI: 10.1007/s00203-004-0681-5
Source: PubMed

ABSTRACT

Pseudomonas putida GJ31 harbors a degradative pathway for chlorobenzene via meta-cleavage of 3-chlorocatechol. Pseudomonads using this route for chlorobenzene degradation, which was previously thought to be generally unproductive, were isolated from various contaminated environments of distant locations. The new isolates, Pseudomonas fluorescens SK1 (DSM16274), Pseudomonas veronii 16-6A (DSM16273), Pseudomonas sp. strain MG61 (DSM16272), harbor a chlorocatechol 2,3-dioxygenase (CbzE). The cbzE-like genes were cloned, sequenced, and expressed from the isolates and a mixed culture. The chlorocatechol 2,3-dioxygenases shared 97% identical amino acids with CbzE from strain GJ31, forming a distinct family of catechol 2,3-dioxygenases. The chlorocatechol 2,3-dioxygenase, purified from chlorobenzene-grown cells of strain SK1, showed an identical N-terminal sequence with the amino acid sequence deduced from cloned cbzE. In all investigated chlorobenzene-degrading strains, cbzT-like genes encoding ferredoxins are located upstream of cbzE. The sequence data indicate that the ferredoxins are identical (one amino acid difference in CbzT of strain 16-6A compared to the others). In addition, the structure of the operon downstream of cbzE is identical in strains GJ31, 16-6A, and SK1 with genes cbzX (unknown function) and the known part of cbzG (2-hydroxymuconic semialdehyde dehydrogenase) and share 100% nucleotide sequence identity with the entire downstream region. The current study suggests that meta-cleavage of 3-chlorocatechol is not an atypical pathway for the degradation of chlorobenzene.

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    • "Consequently, 2-haloalkanoic acid dehalogenase may be worthy for its bioremediation mechanism for different haloacid pollutants. Many microorganisms can break down halogenated compounds by cleaving their carbon-halogen bonds via dehalogenase-catalyzed reactions and, therefore, may aid in the removal of organohalides pollutant from the environment [5] [6] [7]. These dehalogenase enzymes are broadly classified as haloalkane dehalogenases, halohydrin dehalogenases, haloacetate dehalogenases, dichloromethane dehalogenases, and D-and L-haloalkanoic acid dehalogenases based on their cleavage nature [8] [9]. "
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    • "The gene encoding this dioxygenase (cbzE) is preceded by a xylT-like gene called cbzT. The same is true for other chlorobenzene-degrading strains using the meta-cleavage pathway (Göbel et al., 2004). The CbzE enzyme was found to undergo inactivation during catalysis of 4-methylcatechol cleavage, suggesting that the loss of activity resulted from an oxidation of the active site iron as shown for C23O mt-2 . "
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