Characterization of 2,2-DCP degrading ability of halotolerant bacteria and its dehalogenase structural analysis
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Date
2017
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Universiti Teknologi Malaysia
Abstract
In view of the potential long-term risks that halogenated compounds may pose on the well being of humans and the environment, due to their recalcitrance and persistent toxicity, the quest of isolating effective microorganisms capable of degrading these substances merits urgent consideration. In this study, a bacterial strain was isolated from marine environment of Desaru Beach, Malaysia, subsequently identified as Pseudomonas aeruginosa MX1. The strain was efficient in degrading 2,2-dichloropropionic acid at only relatively low concentrations of NaCl (< 5%). However, due to the escalating manufacturing activities and unscrupulous dumping of industrial effluents into marine environment, we also compared degradation efficiency of such substances by a novel dehalogenase-producing bacterium (determined by 16S rDNA sequence and biochemical characteristics as Pseudomonas halophila HX) isolated from hypersaline environment of Tuz Gölü Lake, Turkey. Under optimal culture conditions (pH 8.0, 15% NaCl, 30°C, 200 rpm, 96 h), the strain almost completely degraded 99.3% of 2,2-dichloropropionic acid (20 mM). In view of its catalytic efficiency, the dehalogenase gene (dehHX) was PCRamplified to acquire the DehHX deduced amino acid sequence. The DehHX was found to belong to Group I dehalogenase with a 82% sequence identity to dehalogenase DehI from Pseudomonas putida strain PP3. Interestingly, the study found the DehHX amino acid composition was more acidic (pI, 3.89) than the nonhalophilic dehalogenases (average measured pI = 6.16). Homology-based structural modeling revealed that the surface charge of DehHX was unusually negative, signifying adapted evolutionary of the P. halophila toward its hypersaline environment. Based on such findings, it can be construed that bio-prospecting for efficient halogen–degrading microorganisms in highly saline environments may possibly be a safer and sustainable means for bioremediation of contaminated coastal areas which is an increasingly common worldwide problem
Description
Thesis (PhD. (Biosciences))
Keywords
Halogen compounds, Hazardous waste site remediation—Research, Hazardous wastes—Biodegradation
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