Degradation of 1,2-Dibromoethane by Mycobacterium sp. Strain GP1

Abstract

The newly isolated bacterial strain GP1 can utilize 1,2-dibromoethane as the sole carbon and energy source. On the basis of 16S rRNA gene sequence analysis, the organism was identified as a member of the subgroup which contains the fast-growing mycobacteria. The first step in 1,2-dibromoethane metabolism is catalyzed by a hydrolytic haloalkane dehalogenase. The resulting 2-bromoethanol is rapidly converted to ethylene oxide by a haloalcohol dehalogenase, in this way preventing the accumulation of 2-bromoethanol and 2-bromoacetaldehyde as toxic intermediates. Ethylene oxide can serve as a growth substrate for strain GP1, but the pathway(s) by which it is further metabolized is still unclear. Strain GP1 can also utilize 1-chloropropane, 1-bromopropane, 2-bromoethanol, and 2-chloroethanol as growth substrates. 2-Chloroethanol and 2-bromoethanol are metabolized via ethylene oxide, which for both haloalcohols is a novel way to remove the halide without going through the corresponding acetaldehyde intermediate. The haloalkane dehalogenase gene was cloned and sequenced. The dehalogenase (DhaAf) encoded by this gene is identical to the haloalkane dehalogenase (DhaA) of Rhodococcus rhodochrous NCIMB 13064, except for three amino acid substitutions and a 14-amino-acid extension at the C terminus. Alignments of the complete dehalogenase gene region of strain GP1 with DNA sequences in different databases showed that a large part of adhaA gene region, which is also present in R. rhodochrous NCIMB 13064, was fused to a fragment of a haloalcohol dehalogenase gene that was identical to the last 42 nucleotides of thehheB gene found in Corynebacterium sp. strain N-1074.

Bacterial degradation of xenobiotic compounds: evolution and distribution of novel enzyme activities

“…In the first place, enrichment of 1,2-dibromoethane degrading bacteria has yielded, after much patience, a culture that can slowly grow with 1,2-dibromoethane as sole carbon source. This Mycobacterium strain produces a haloalkane dehalogenase that is almost identical to DhaA, but there are three substitutions (C176F, P248S, Y272F), and, most remarkably, on the C-terminal side the enzyme is 14 amino acids longer due to an in-frame fusion of the 3′ end of the dehalogenase gene with 42 bases that encode the last 14 amino acids of a halohydrin dehalogenase (hheB gene) (Poelarends et al, 1999). Thus, this chimeric dehalogenase is 307 amino acids long instead of the 293 amino acids of the standard Rhodocccus enzyme.…”

Biochemical and biophysical characterisation of haloalkane dehalogenases DmrA and DmrB in Mycobacterium strain JS60 and their role in growth on haloalkanes

“…The first HLDs were discovered in bacteria from contaminated sites, which were isolated using haloalkanes as the carbon and energy source. In such bacteria, the role of the HLDs is clear (Keuning et al, 1985;Poelarends et al, 1999). In recent years, genome sequencing has revealed hundreds of putative HLD genes in diverse species, including bacteria from pristine environmental samples (Hesseler et al, 2011), and human pathogens such as Mycobacterium tuberculosis H37Rv (Jesenska et al, 2000).…”

Occurrence and community composition of fast-growing Mycobacterium in soils contaminated with polycyclic aromatic hydrocarbons

“…In spite of the limited bioavailability and poor biodegradability of PAHs, different bacteria, often mycobacteria, have been isolated that are able to use PAHs as sole sources of carbon and energy [2][3][4][5][6][7]. So far, all PAH-biodegrading Mycobacterium isolates [2][3][4][5][6][7][8][9][10][11] have been placed in the phylogenetic branch of the Ôfast-growing mycobacteriaÕ. In the Mycobacterium phylogenetic tree, the Ôfast-growing mycobacteriaÕ form a coherent line of descent, distinct from the more recently evolved slow-growers, within which the wellknown mycobacterial pathogens are clustered [12][13][14][15].…”