Isolation of Klebsiella pneumoniae from Sungai Skudai and in silico analysis of putative dehalogenase protein

Aims@#The surplus use of herbicide Dalapon® contains 2,2-dichloropropionic acid (2,2-DCP) poses great danger to human and ecosystem due to its toxicity. Hence, this study focused on the isolation and characterization of a dehalogenase producing bacteria from Sungai Skudai, Johor, capable of utilizing 2,2-DCP as a carbon source and in silico analysis of its putative dehalogenase.@*Methodology and results@#Isolation of the target bacteria was done by using 2,2-DCP-enriched culture as the sole carbon source that allows a bacterium to grow in 20 mM of 2,2-DCP at 30 °C with the corresponding doubling time of 8.89 ± 0.03 h. The isolated bacterium was then designated as Klebsiella pneumoniae strain YZ based on biochemical tests and basic morphological examination. The full genome of K. pneumoniae strain KLPN_25 (accession number: RRE04903) which obtained from NCBI database was screened for the presence of dehalogenase gene, assuming both strains YZ and KLPN_25 were the same organisms. A putative dehalogenase gene was then identified as type II dehalogenase from the genome sequence of strain KLPN_25. The protein structure of the type II dehalogenase of KLPN_25 strain was then pairwise aligned with the crystal structure of L-2-haloacid dehalogenase (L-DEX) Pseudomonas sp. strain YL as the template, revealing the existence of conserved amino acids residues, uniquely known to participate in the dehalogenation mechanism. The finding thus implies that the amino acid residues of type II dehalogenase possibly shares similar catalytic functions with the L-DEX.@*Conclusion, significance and impact of the study@#In conclusion, this study confirmed the presence of new dehalogenase from the genus Klebsiella with potential to degrade 2,2-DCP from the river water. The structural information of type II dehalogenase provides insights for future work in designing haloacid dehalogenases.

Dehalogenase producing bacteria from extreme environment: A review

@#Halogenated compounds create the most important class of xenobiotic which commonly lead to pollution. Some of these compounds are very toxic and cause enormous problems to human health and to the environment. Many of these toxic chemicals have been shown to occur in various extreme habitats. Pollutant-degrading microorganisms, adapted to grow in various environments, play an important role in the biological treatment of polluted extreme habitats. The presence of dehalogenase producing microorganisms in extreme habitat in particular is necessary since the enzyme can catalyze the removal of a halogen atom from a substrate. Therefore, it can reduce the toxicity of the halogenated compound and some are of interest for study in industrial application. Thermophiles, psychrophiles, acidophiles, alkaliphiles and halophiles are types of extremophiles. Knowledge of the biodegradation of toxic chemicals in extreme environment is limited. Here, examples of dehalogenase producing bacteria isolated from various extreme conditions and its special characteristics/features will be discussed in this review.

Microbial isolation and degradation of selected haloalkanoic aliphatic acids by locally isolated bacteria: A review

The liberation of halogenated compounds by both natural processes and man-made activities has led to extensive contamination of the biosphere. Bioremediation via the dehalogenation process offers a sustainable way to eliminate such hazardous contaminants. Whereas, a large number of natural soil microorganisms (i.e., bacteria and fungi) that have been isolated are capable of degrading and detoxifying such contaminants, information on the preferred types of halogenated compounds that they catalyze is lacking. In this review, we discuss those microorganisms that have the potential to perform bioremediation of such environmental contaminants. We also present a method for isolating novel dehalogenase-producing microorganisms from cow dung.

Isolation and identification of bacteria isolated from ruminant animal waste that able to degrade 2,2-dichloropropionic acid (2,2-DCP)

Aims: A 2,2-dichloropropionic acid (2,2-DCP) naturally degrading bacterial species, strain SN1 was successfully isolated from cow dung capable of utilizing the substance as the sole carbon source and energy. Methodology and results: Strain SN1 was preferred over other strains (SN2, SN3 and SN4) following observations on its rapid growth in 20 mM 2,2-DCP liquid minimal media. Since strain SN1 clearly exhibited tolerance towards 2,2-DCP, its growth in various concentrations (10 mM, 20 mM, 30 mM and 40 mM) of the substance was evaluated. The study found the bacteria grew particularly well in 20 mM 2,2-DCP with the highest chloride release of 39.5 µmole Cl- /mL while exhibiting a remarkably short doubling time of 3.85 h. In view of such notable characteristics, species identification via Biolog GEN III system and 16S rRNA analysis was performed and established strain SN1 as Bacillus cereus. Conclusion, significance and impact of study: Considering the rapid growth of B. cereus strain SN1 in such medium, its employment as a bioremediation agent to treat 2,2-DCP contaminated soils may prove beneficial. Moreover, this is the first reported case of a Bacillus sp. isolated from cow dung capable of utilizing 2,2-DCP. Therefore, further assessment into its ability to degrade other types of haloalkanoic acids merit special consideration.

Formação de subprodutos orgânicos halogenados nas operações de pré-oxidação com cloro, ozônio e peroxônio e pós-cloração em água conténdo subtância húmica / Formation of halogenated organic byproducts using preoxidation with chlorine, ozone and peroxone and post-chlorination of water containing humic substances

Dentre os compostos orgânicos halogenados que podem ser encontrados na água distribuída à população, destacam-se: trialometanos, ácidos haloacéticos, haloaldeídos, halocetonas, halofenóis e halopicrinas. O presente trabalho teve como objetivo avaliar o efeito da formação de 22 subprodutos com a utilização dos pré-oxidantes: cloro, ozônio e peroxônio. A formação de subprodutos foi observada em água preparada com adição de substâncias húmicas extraídas de solo turfoso, por meio do uso da pré-oxidação, presença e ausência de coagulação, filtração e pós-cloração. Os subprodutos foram quantificados por cromatografia gasosa com detetor de captura de elétrons. Os resultados obtidos mostraram que o uso de pré-oxidantes alternativos, ozônio e peroxônio, associados à coagulação, filtração e pós-cloração, formam quantidades pequenas de subprodutos.

When chlorine is used as preoxidant, the formation of halogenated organic byproducts found in water treated and distriduted to the population, are: trihalometane, haloacetic acids, haloaldehyde, haloketone, halophenol and halopicrin. This research was performed to evaluate the formation potential of 22 byproducts using the following preoxidants: chlorine, ozone and peroxone. The formation of byproducts was simulated in water prepared with the addition of humic substances extracted from peat soil by the use of preoxidants, coagulation, filtration, and post-chlorination. Byproducts have quantified by gas chromatography with electron capture detector. The results obtained showed that the use of alternative preoxidants, such as ozone and peroxone, associated with coagulation, filtration, and post-chlorination form a low concentration of byproducts.