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- Genetic Organization of the dhlA Gene Encoding 1,2-Dichloroethane Dechlorinase from Xanthobacter flavus UE15
- Ji-Sook Song , Dong-Hun Lee , Kyoung Lee , Chi-Kyung Kim
- J. Microbiol. 2004;42(3):188-193.
- DOI: https://doi.org/2091 [pii]
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Abstract
- Xanthobacter flavus strain UE15 was isolated in wastewater obtained from the Ulsan industrial complex, Korea. This strain functions as a 1,2-dichloroethane (1,2-DCA) degrader, via a mechanism of hydrolytic dechlorination, under aerobic conditions. The UE15 strain was also capable of dechlorinating other chloroaliphatics, such as 2-chloroacetic acid and 2-chloropropionic acid. The dhlA gene encoding 1,2-DCA dechlorinase was cloned from the genomic DNA of the UE15 strain, and its nucleotide sequence was determined to consist of 933 base pairs. The deduced amino acid sequence of the DhlA dechlorinase exhibited 100% homology with the corresponding enzyme from X. autotrophicus GJ10, but only 27 to 29% homology with the corresponding enzymes from Rhodococcus rhodochrous, Pseudomonas pavonaceae, and Mycobacterium sp. strain GP1, which all dechlorinate haloalkane compounds. The UE15 strain has an ORF1 (1,356 bp) downstream from the dhlA gene. The OFR1 shows 99% amino acid sequence homology with the transposase reported from X. autotrophicus GJ10. The transposase gene was not found in the vicinity of the dhlA in the GJ10 strain, but rather beside the dhlB gene coding for haloacid dechlorinase. The dhlA and dhlB genes were confirmed to be located at separate chromosomal loci in the Xanthobacter flavus UE15 strain as well as in X. autotrophicus GJ10. The dhlA and transposase genes of the UE15 strain were found to be parenthesized by a pair of insertion sequences, IS1247, which were also found on both sides of the transposase gene in the GJ10 strain. This unique structure of the dhlA gene organization in X. flavus strain UE15 suggested that the dechlorinase gene, dhlA, is transferred with the help of the transposase gene.
- Characteristics of Several Bacterial Isolates Capable of Degrading Chloroaliphatic Compounds via Hydrolytic Dechlorination
- Ji-Sook Song , Dong-Hun Lee , Kyoung Lee , Chi-Kyung Kim
- J. Microbiol. 2003;41(4):277-283.
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Abstract
- Haloaliphatic hydrocarbons have been widely used as solvents and ingredients of pesticides and herbicides. However, when these compounds contaminate the environment, they can be very hazardous to animals and humans because of their potential toxicity and carcinogenicity. Therefore, lots of studies have been made for microbial degradation of those pollutant chemicals. In this study, 11 bacterial strains capable of degrading 1,2-dichloroethane (1,2-DCA), 2-chloropropionic acid (2-CPA), 2,3-dichloropropionic acid (2,3-DCPA), and 2-monochloroacetic acid (2-MCA) by hydrolytic dechlorination under aerobic conditions were isolated from wastewaters and rice paddy soil samples. Their morphological and biochemical characteristics and their degradation capabilities of haloaliphatic hydrocarbons were examined. On the basis of the 16S rDNA sequences, 8 different kinds of microbial species, including Pseudomonas plecoglossicida, Xanthobacter flavus, Ralstonia eutropha, were identified. All of the isolated strains can degrade MCA. In particular, strains UE-2 and UE-15 degraded 1,2-DCA, and strain CA-11 degraded 2,3-DCPA, which are hardly degraded by other strains.
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