Degradation of 1,2-dibromoethane by Mycobacterium sp. strain GP1

The newly isolated bacterial strain GP1 can utilize 1,2-dibromoethane as th e sole carbon and energy source. On the basis of 16S rRNA gene sequence ana lysis, the organism was identified as a member of the subgroup which contai ns the fast-growing mycobacteria, The first step in 1,2-dibromoethane metab olism is catalyzed by a hydrolytic haloalkane dehalogenase, The resulting 2 -bromoethanol is rapidly converted to ethylene oxide by a haloalcohol dehal ogenase, in this way preventing the accumulation of 2-bromoethanol and 2-br omoacetaldehyde as toxic intermediates. Ethylene oxide can serve as a growt h substrate for strain GP1, but the pathway(s) by which it is further metab olized is still unclear. Strain GP1 can also utilize 1-chloropropane, 1-bro mopropane, 2-bromoethanol, and 2-chloroethanol as growth substrates, 2-Chlo roethanol and 2-bromoethanol are metabolized via ethylene oxide, which for both haloalcohols is a no,el way to remove the halide without going through the corresponding acetaldehyde intermediate, The haloalkane dehalogenase g ene was cloned and sequenced. The dehalogenase (DhaA(f)) encoded by this ge ne is identical to the haloalkane dehalogenase (DhaA) of Rhodococcus rhodoc hrous 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 a dhaA gene region, which Is also present in R. rhodoc hrous NCIMB 13064, was fused to a fragment of a haloalcohol dehalogenase ge ne that was identical to the last 42 nucleotides of the hheB gene found in Corynebacterium sp, strain N-1074.