Microbiological methods for the cleanup of soil and ground water contaminated with halogenated organic compounds

Morgan, Phil G.; Watkinson, R. J.

doi:10.1111/j.1574-6968.1989.tb03401.x

Cited by 50 publications

(47 citation statements)

References 150 publications

(177 reference statements)

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“…It is important to obtain a more fundamental understanding of the pMMO because of the importance of methanotrophs in the global methane cycle (32) and the fact that the majority of known methanotrophs contain only the pMMO. Furthermore, methanotrophs have been proposed for the in situ bioremediation of sites contaminated with small halogenated solvents (28,41), and the pMMO can degrade halogenated hydrocarbons, including trichloroethylene (12).…”

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Particulate methane monooxygenase genes in methanotrophs

et al. 1995

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A 45-kDa membrane polypeptide that is associated with activity of the particulate methane monooxygenase (pMMO) has been purified from three methanotrophic bacteria, and the N-terminal amino acid sequence was found to be identical in 17 of 20 positions for all three polypeptides and identical in 14 of 20 positions for the N terminus of AmoB, the 43-kDa subunit of ammonia monooxygenase. DNA from a variety of methanotrophs was screened with two probes, an oligonucleotide designed from the N-terminal sequence of the 45-kDa polypeptide from Methylococcus capsulatus Bath and an internal fragment of amoA, which encodes the 27-kDa subunit of ammonia monooxygenase. In most cases, two hybridizing fragments were identified with each probe. Three overlapping DNA fragments containing one of the copies of the gene encoding the 45-kDa pMMO polypeptide (pmoB) were cloned from Methylococcus capsulatus Bath. A 2.1-kb region was sequenced and found to contain both pmoB and a second gene, pmoA. The predicted amino acid sequences of these genes revealed high identity with those of the gene products of amoB and amoA, respectively. Further hybridization experiments with DNA from Methylococcus capsulatus Bath and Methylobacter albus BG8 confirmed the presence of two copies of pmoB in both strains. These results suggest that the 45-and 27-kDa pMMO-associated polypeptides of methanotrophs are subunits of the pMMO and are present in duplicate gene copies in methanotrophs.Methanotrophs are a group of gram-negative bacteria that utilize methane as their sole source of carbon and energy. The initial transformation involves the conversion of methane into methanol by methane monooxygenase (MMO):

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Particulate methane monooxygenase genes in methanotrophs

et al. 1995

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“…Kinetic parameters for the mineralization of propachlor were determined as previously reported (11). Metabolism was determined by measuring 14 CO 2 released from [ring-U- 14 C]propachlor (12 Ci/ mol). Cells pregrown in MB and glucose or propachlor were washed and resuspended in 10 ml of phosphate buffer (pH 7.2); 5 ml of the phosphate buffer was added to 50-ml flasks containing 1 Ci of [ring-U- 14 C]propachlor.…”

Section: Methodsmentioning

confidence: 99%

“…Metabolism was determined by measuring 14 CO 2 released from [ring-U- 14 C]propachlor (12 Ci/ mol). Cells pregrown in MB and glucose or propachlor were washed and resuspended in 10 ml of phosphate buffer (pH 7.2); 5 ml of the phosphate buffer was added to 50-ml flasks containing 1 Ci of [ring-U- 14 C]propachlor. Different amounts of unlabeled propachlor were added to the flasks to achieve final concentrations ranging from 0.1 to 2 mM.…”

Section: Methodsmentioning

confidence: 99%

“…Cells pregrown on propachlor or glucose were used to study the kinetics of propachlor metabolism. Glucose-grown cells produced 14 14 CO 2 was measured as a product from the carbon atoms in the propachlor ring; no significant 14 CO 2 was released in control experiments without cells, and no counts were measured in controls without radioactivity. Thus, propachlor could be completely degraded by Pseudomonas strain GCH1, and the propachlor metabolism was constitutive.…”

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Propachlor Removal by Pseudomonas Strain GCH1 in an Immobilized-Cell System

Martín

Mengs

Płaza

et al. 2000

Appl Environ Microbiol

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A bacterial strain capable of growing on propachlor (2-chloro-N-isopropylacetanilide) was isolated from soil by using enrichment and isolation techniques. The strain isolated, designated GCH1, was classified as a member of the genus Pseudomonas. Washed-cell suspensions of strain GCH1 accumulated N-isopropylacetanilide, acetanilide, acetamide, and catechol. Pseudomonas strain GCH1 grew on propachlor with a generation time of 4.2 h and a rate of substrate utilization of 1.75 ؎ 0.15 mol h ؊1 . Gene expression did not require induction but was subject to catabolite expression. Acetanilide was a growth substrate with a yield of 0.56 ؎ 0.02 mg of protein mol ؊1 . GCH1 strain cells were immobilized by adsorption onto a ceramic support and were used as biocatalysts in an immobilized cell system. Propachlor elimination reached 98%, with a retention time of 3 h and an initial organic load of 0.5 mM propachlor. The viability of immobilized cells increased 34-fold after 120 days of bioreactor operation.Propachlor (2-chloro-N-isopropylacetanilide) is an acylanilide herbicide widely used with corn, onion, cabbage, rose bushes, and ornamental plants. Microbial degradation (11,15,16,19) is the primary mechanism of acylanilide dissipation from soil. We previously reported the isolation of Pseudomonas strain PEM1 (3, 10, 11), which metabolizes the herbicide propachlor, yielding N-isopropylacetanilide, acetanilide, and acetamide as intermediates, and the isolation of Acinetobacter strain BEM2, which follows a different pathway and yields N-isopropylaniline and isopropylamine as intermediates. Lee et al. (9) reported that N-isopropylaniline, N-isopropylacetanilide, N-(1-hydroxyisopropyl)acetanilide, and N-isopropyl-2-acetoxyacetanilide were formed in soil treated with propachlor. Villareal et al. (18) proposed a propachlor degradative pathway yielding 2-chloro-N-isopropylacetamide and catechol as intermediates.Groundwater and soil contamination by herbicides has recently become of increasing concern (6,7,20). The relatively new concept of bioremediation provides a potentially cheap alternative to traditional disposal techniques, in addition to representing a genuine removal of contaminants by microbial degradation rather than the relocation of contaminants in such processes as landfilling. The problems presented by continuous fermentation processes could be resolved by the use of immobilized cells as biocatalysts (5,7,12,21).The aim of this study was to characterize the propachlor metabolism of a strain (GCH1) isolated from soil and to test a bioremediation system using immobilized cells in a reactor operating over a period of 150 days. The kinetics of the degradation and the viability of the immobilized cells are reported. MATERIALS AND METHODSIsolation of bacteria. Ten soil samples (10) were collected from agricultural fields in Madrid, Spain, with a history of propachlor contamination. Minimal medium (MB) (4) supplemented with 45 mg of propachlor liter Ϫ1 was inoculated with 20 g of soil sample and incubated at 28°C without sh...

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“…Alternatively, degradational activity may be a purely cometabolic process, with the responsible methylotrophs deriving little or no direct benefit from the process (Morgan and Watkinson 1989).…”

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confidence: 99%