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James M Tiedje - One of the best experts on this subject based on the ideXlab platform.
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degradation of Aroclor 1242 dechlorination products in sediments by burkholderia xenovorans lb400 ohb and rhodococcus sp strain rha1 fcb
Applied and Environmental Microbiology, 2006Co-Authors: Jorge L M Rodrigues, John F Quensen, Alan C Kachel, Michael R Aiello, Olga V Maltseva, Tamara V Tsoi, James M TiedjeAbstract:Approximately 635 million kg of polychlorinated biphenyls (PCBs) were produced in the United States from 1929 to 1978, and a similar amount was manufactured in Japan, Europe, and the former USSR (19). Of the total amount, it is estimated that 31% has been released into the environment, contaminating soils and sediments (16). The high hydrophobicities of PCB molecules contribute to their accumulation in higher-trophic-level species and their long-term environmental persistence. Over the past 30 years, research on PCBs has shown that these compounds, previously thought to be recalcitrant, can be degraded by both anaerobic and aerobic bacteria. Under anaerobic conditions, anaerobic microbial consortia convert highly chlorinated congeners into less chlorinated biphenyls by reductive dechlorination, leaving the rings intact (3, 7, 30, 31). Under aerobic conditions, some microorganisms with more versatile oxidative capabilities can cleave lesser chlorinated biphenyl rings to yield chlorinated benzoates and pentanoic acid derivatives (28), which are often degradable by other bacteria. Hence, a sequential anaerobic/aerobic microbial process has the potential for the complete biodegradation of PCBs (25). Such a sequence could enable natural attenuation at aerobic-anaerobic interfaces (9) as well as be developed into a PCB bioremediation technology (37, 39). Because of their abilities to attack a wide range of PCB congeners, Burkholderia xenovorans LB400 and Rhodococcus sp. strain RHA1 are two of the more promising strains for use in the aerobic stage of a PCB biotreatment process. However, as is true of other PCB-degrading microorganisms, at best they have limited ability to grow on PCBs (29), so repeated additions (bioaugmentation) would be required for biotreatment. Both strains accumulate chlorobenzoates during PCB degradation. We reasoned that by adding genes for the dechlorination of chlorobenzoates, we could enable these strains to grow on PCBs well enough to avoid the need for repeated bioaugmentation. We have previously demonstrated this approach by separately transferring ortho (ohb) and para (fcb) chlorobenzoate-dechlorinating genes to Comamonas testosteroni VP44, obtaining constructs capable of growth on 4-chlorobenzoate (4-CBA) and 4-chlorobiphenyl (4-CB) or 2-CBA and 2-CB (17). Similarly, we transferred fcb genes to RHA1, enabling it to grow on 4-CBA and 4-CB (33). While there have been many experiments testing the ability of various aerobic bacteria to degrade PCBs, most of the work employed only one congener (27), employed a freshly applied contaminant (21), and/or was carried out under resting cell conditions (1, 26). While providing useful information, these types of experiments do not reflect the conditions under which aerobic bacteria have to perform in a biotreatment process for PCBs. PCB-contaminated sites contain a full spectrum of congeners coming from Aroclor spills, and the lengthy time they have usually had to partition into soil or sediment organic matter makes them less bioavailable than freshly spiked PCBs. Furthermore, PCB-degrading bacterial strains added to PCB-contaminated soil or sediment have to compete effectively with the indigenous soil microorganisms. These factors need to be taken into account in assessing the suitability of aerobic PCB-degrading microorganisms for use in a biotreatment process. The work reported here is an extension of our approach of adding chlorobenzoate-degrading capabilities to competent PCB-degrading microorganisms, coupled with an evaluation of the constructs obtained for use in the aerobic stage of a sequential anaerobic/aerobic biotreatment process for PCBs. We introduced ohb genes into LB400 and tested the construct first for its ability to grow on 2-chlorobenzoate and then for its ability to degrade and grow on selected PCB congeners typically formed from the microbial dechlorination of Aroclors. Finally, we simulated a sequential anaerobic/aerobic biotreatment process by dechlorinating Aroclor 1242 in anaerobic sediment slurries, establishing aerobic conditions, and adding LB400(ohb) and RHA1(fcb) together to the sediments. The constructs remained genetically stable and degraded 57% of the remaining PCBs while growing in number, successfully competing with indigenous bacteria.
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degradation of anaerobic reductive dechlorination products of Aroclor 1242 by four aerobic bacteria
Biodegradation, 1999Co-Authors: Olga V Maltseva, John F Quensen, Tamara V Tsoi, Masao Fukuda, James M TiedjeAbstract:We studied the aerobic degradation of eight PCB congeners which comprise from 70 to 85% of the anaerobic dechlorination products from Aroclor 1242, including 2-, 4-, 2,4-, 2,6-, 2,2'-, 2,4'-, 2,2', 4-, and 2,4,4'-chlorobiphenyl (CB), and the biodegradation of their mixtures designed to simulate anaerobic dechlorination profiles M and C. Strains Comamonas testosteroni VP44 and Rhodococcus erythreus NY05 preferentially oxidized a para-substituted ring, while Rhodococcus sp. RHA1, similar to well known strain Burkholderia sp. LB400, preferably attacked an ortho-chlorinated ring. Strains with ortho-directed attack extensively degraded 2,4'- and 2,4,4'-CB into 4-chlorobenzoate, while bacteria with para-directed attack transformed these congeners mostly into potentially problematic meta-cleavage products. The strains that preferentially oxidized an ortho-substituted ring readily degraded seven of the eight congeners supplied individually; only 2,6-CB was poorly degraded. Degradation of 2,2'- and 2,4,4'-CB was reduced when present in mixtures M and C. Higher efficiencies of degradation of the individual congeners and defined PCB mixtures M and C and greater production of chlorobenzoates were observed with bacteria that preferentially attack an ortho-substituted ring. PCB congeners 2,4'-, 2,2',4-, and 2,4,4'-CB can be used to easily identify bacteria with ortho-directed attack which are advantageous for use in the aerobic stage of the two-phase (anaerobic/aerobic) PCB bioremediation scheme.
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reductive debromination of the commercial polybrominated biphenyl mixture firemaster bp6 by anaerobic microorganisms from sediments
Applied and Environmental Microbiology, 1992Co-Authors: P J Morris, John F Quensen, James M Tiedje, Stephen A BoydAbstract:Anaerobic microorganisms eluted from three sediments, one contaminated with polybrominated biphenyls (PBBs) and two contaminated with polychlorinated biphenyls, were compared for their ability to debrominate the commercial PBB mixture Firemaster. These microorganisms were incubated with reduced anaerobic mineral medium and noncontaminated sediment amended with Firemaster. Firemaster averages six bromines per biphenyl molecule; four of the bromines are substituted in the meta or para position. The inocula from all three sources were able to debrominate the meta and para positions. Microorganisms from the Pine River (St. Louis, Mich.) contaminated with Firemaster, the Hudson River (Hudson Falls, N.Y.) contaminated with Aroclor 1242, and Silver Lake (Pittsfield, Mass.) contaminated with Aroclor 1260 removed 32, 12, and 3% of the meta plus para bromines, respectively, after 32 weeks of incubation. This suggests that previous environmental exposure to PBBs enhances the debromination capability of the sediment microbial community through selection for different strains of microorganisms. The Pine River inoculum removed an average of 1.25 bromines per biphenyl molecule during a 32-week incubation period, resulting in a mixture potentially more accessible to aerobic degradation processes. No ortho bromine removal was observed. However, when Firemaster was incubated with Hudson River microorganisms that had been repeatedly transferred on a pyruvate medium amended with Aroclor 1242, 17% of the meta and para bromines were removed after 16 weeks of incubation and additional debromination products, including 2-bromobiphenyl and biphenyl, were detected. This suggests the possibility for ortho debromination, since all components of the Firemaster mixture have at least one ortho-substituted bromine.(ABSTRACT TRUNCATED AT 250 WORDS)
John F Quensen - One of the best experts on this subject based on the ideXlab platform.
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degradation of Aroclor 1242 dechlorination products in sediments by burkholderia xenovorans lb400 ohb and rhodococcus sp strain rha1 fcb
Applied and Environmental Microbiology, 2006Co-Authors: Jorge L M Rodrigues, John F Quensen, Alan C Kachel, Michael R Aiello, Olga V Maltseva, Tamara V Tsoi, James M TiedjeAbstract:Approximately 635 million kg of polychlorinated biphenyls (PCBs) were produced in the United States from 1929 to 1978, and a similar amount was manufactured in Japan, Europe, and the former USSR (19). Of the total amount, it is estimated that 31% has been released into the environment, contaminating soils and sediments (16). The high hydrophobicities of PCB molecules contribute to their accumulation in higher-trophic-level species and their long-term environmental persistence. Over the past 30 years, research on PCBs has shown that these compounds, previously thought to be recalcitrant, can be degraded by both anaerobic and aerobic bacteria. Under anaerobic conditions, anaerobic microbial consortia convert highly chlorinated congeners into less chlorinated biphenyls by reductive dechlorination, leaving the rings intact (3, 7, 30, 31). Under aerobic conditions, some microorganisms with more versatile oxidative capabilities can cleave lesser chlorinated biphenyl rings to yield chlorinated benzoates and pentanoic acid derivatives (28), which are often degradable by other bacteria. Hence, a sequential anaerobic/aerobic microbial process has the potential for the complete biodegradation of PCBs (25). Such a sequence could enable natural attenuation at aerobic-anaerobic interfaces (9) as well as be developed into a PCB bioremediation technology (37, 39). Because of their abilities to attack a wide range of PCB congeners, Burkholderia xenovorans LB400 and Rhodococcus sp. strain RHA1 are two of the more promising strains for use in the aerobic stage of a PCB biotreatment process. However, as is true of other PCB-degrading microorganisms, at best they have limited ability to grow on PCBs (29), so repeated additions (bioaugmentation) would be required for biotreatment. Both strains accumulate chlorobenzoates during PCB degradation. We reasoned that by adding genes for the dechlorination of chlorobenzoates, we could enable these strains to grow on PCBs well enough to avoid the need for repeated bioaugmentation. We have previously demonstrated this approach by separately transferring ortho (ohb) and para (fcb) chlorobenzoate-dechlorinating genes to Comamonas testosteroni VP44, obtaining constructs capable of growth on 4-chlorobenzoate (4-CBA) and 4-chlorobiphenyl (4-CB) or 2-CBA and 2-CB (17). Similarly, we transferred fcb genes to RHA1, enabling it to grow on 4-CBA and 4-CB (33). While there have been many experiments testing the ability of various aerobic bacteria to degrade PCBs, most of the work employed only one congener (27), employed a freshly applied contaminant (21), and/or was carried out under resting cell conditions (1, 26). While providing useful information, these types of experiments do not reflect the conditions under which aerobic bacteria have to perform in a biotreatment process for PCBs. PCB-contaminated sites contain a full spectrum of congeners coming from Aroclor spills, and the lengthy time they have usually had to partition into soil or sediment organic matter makes them less bioavailable than freshly spiked PCBs. Furthermore, PCB-degrading bacterial strains added to PCB-contaminated soil or sediment have to compete effectively with the indigenous soil microorganisms. These factors need to be taken into account in assessing the suitability of aerobic PCB-degrading microorganisms for use in a biotreatment process. The work reported here is an extension of our approach of adding chlorobenzoate-degrading capabilities to competent PCB-degrading microorganisms, coupled with an evaluation of the constructs obtained for use in the aerobic stage of a sequential anaerobic/aerobic biotreatment process for PCBs. We introduced ohb genes into LB400 and tested the construct first for its ability to grow on 2-chlorobenzoate and then for its ability to degrade and grow on selected PCB congeners typically formed from the microbial dechlorination of Aroclors. Finally, we simulated a sequential anaerobic/aerobic biotreatment process by dechlorinating Aroclor 1242 in anaerobic sediment slurries, establishing aerobic conditions, and adding LB400(ohb) and RHA1(fcb) together to the sediments. The constructs remained genetically stable and degraded 57% of the remaining PCBs while growing in number, successfully competing with indigenous bacteria.
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Inhibition of LPS-induced splenocyte proliferation by ortho-substituted polychlorinated biphenyl congeners.
Toxicology, 2003Co-Authors: L Ashley Smithwick, John F Quensen, Andrew Smith, Allison Stack, Lucille London, Pamela J MorrisAbstract:Polychlorinated biphenyls (PCBs) are persistent environmental contaminants, and their ubiquitous nature has prompted studies of their potential health hazards. As a result of their lipophilic nature, PCBs accumulate in breast milk and subsequently affect the health of offspring of exposed individuals. Biological effects of PCBs in animals have mostly been attributed to coplanar congeners, although effects of ortho congeners also have been demonstrated. To investigate the relationship of immunotoxicity and chlorine substitution pattern, the effects of PCB congeners and mixtures of ortho and non-ortho-substituted constituents of Aroclor 1242 on splenocytes from C57B1/6 mice were examined. The immunotoxic endpoints investigated included splenocyte viability, lipopolysaccharide (LPS)-induced splenocyte proliferation, and LPS-induced antibody secretion. Congeners with multiple ortho chlorines preferentially inhibited splenocyte proliferation as compared with non- or mono-ortho-substituted congeners. However, mixtures of non- and mono-ortho-substituted congeners and multi-ortho-substituted congeners inhibited LPS-induced splenocyte proliferation and antibody secretion at similar concentrations. Exposure of splenocytes to these mixtures did not activate the aryl hydrocarbon receptor (AhR) signal transduction pathway. These results suggest individual multi-ortho-substituted congeners preferentially inhibit LPS-induced splenocyte proliferation, while congeners not exhibiting an effect individually may have additive effects in a mixture to produce an immunotoxic response through an AhR-independent pathway.
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stimulation of contraction of pregnant rat uterus in vitro by non dechlorinated and microbially dechlorinated mixtures of polychlorinated biphenyls
Environmental Health Perspectives, 2001Co-Authors: Jeehyeon Bae, John F Quensen, Stephen A Boyd, Mahmoud A Mousa, Rita LochcarusoAbstract:A previous study of six polychlorinated biphenyl (PCB) congeners showed that PCBs with four or fewer chlorines and ortho substitution stimulate uterine contraction frequency in vitro, whereas congeners with a greater number of chlorines or non-ortho substitution are inactive in vitro. We tested the hypothesis that PCB mixtures stimulate uterine contractions in a manner inversely related to the degree of chlorination and the presence of chlorines in the ortho- position of the biphenyl constituents of the mixtures. Uterine strips from pregnant rats were suspended in standard muscle baths and analyzed for changes in isometric contractions in response to in vitro exposure to commercial PCB mixtures (Aroclors) and their dechlorinated products after microbial degradation. The PCB mixtures Aroclor 1242, 1248, and 1254 significantly stimulated uterine contraction frequency, and the least chlorinated mixture, Aroclor 1242, was the most potent stimulant. Microbes from Hudson River sediment dechlorinated Aroclor 1242 and Aroclor 1254 under reducing conditions to produce mixtures with an increased proportion of ortho-substituted congeners with one or two chlorine substitutions. The PCB mixtures that had undergone microbial reductive dechlorination stimulated uterine contraction frequency to a significantly greater extent than the parent mixtures. These results show that increased uterotonic activity was associated with decreased chlorination and increased ortho substitution of the biphenyl constituents of the mixtures.
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degradation of anaerobic reductive dechlorination products of Aroclor 1242 by four aerobic bacteria
Biodegradation, 1999Co-Authors: Olga V Maltseva, John F Quensen, Tamara V Tsoi, Masao Fukuda, James M TiedjeAbstract:We studied the aerobic degradation of eight PCB congeners which comprise from 70 to 85% of the anaerobic dechlorination products from Aroclor 1242, including 2-, 4-, 2,4-, 2,6-, 2,2'-, 2,4'-, 2,2', 4-, and 2,4,4'-chlorobiphenyl (CB), and the biodegradation of their mixtures designed to simulate anaerobic dechlorination profiles M and C. Strains Comamonas testosteroni VP44 and Rhodococcus erythreus NY05 preferentially oxidized a para-substituted ring, while Rhodococcus sp. RHA1, similar to well known strain Burkholderia sp. LB400, preferably attacked an ortho-chlorinated ring. Strains with ortho-directed attack extensively degraded 2,4'- and 2,4,4'-CB into 4-chlorobenzoate, while bacteria with para-directed attack transformed these congeners mostly into potentially problematic meta-cleavage products. The strains that preferentially oxidized an ortho-substituted ring readily degraded seven of the eight congeners supplied individually; only 2,6-CB was poorly degraded. Degradation of 2,2'- and 2,4,4'-CB was reduced when present in mixtures M and C. Higher efficiencies of degradation of the individual congeners and defined PCB mixtures M and C and greater production of chlorobenzoates were observed with bacteria that preferentially attack an ortho-substituted ring. PCB congeners 2,4'-, 2,2',4-, and 2,4,4'-CB can be used to easily identify bacteria with ortho-directed attack which are advantageous for use in the aerobic stage of the two-phase (anaerobic/aerobic) PCB bioremediation scheme.
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reductive debromination of the commercial polybrominated biphenyl mixture firemaster bp6 by anaerobic microorganisms from sediments
Applied and Environmental Microbiology, 1992Co-Authors: P J Morris, John F Quensen, James M Tiedje, Stephen A BoydAbstract:Anaerobic microorganisms eluted from three sediments, one contaminated with polybrominated biphenyls (PBBs) and two contaminated with polychlorinated biphenyls, were compared for their ability to debrominate the commercial PBB mixture Firemaster. These microorganisms were incubated with reduced anaerobic mineral medium and noncontaminated sediment amended with Firemaster. Firemaster averages six bromines per biphenyl molecule; four of the bromines are substituted in the meta or para position. The inocula from all three sources were able to debrominate the meta and para positions. Microorganisms from the Pine River (St. Louis, Mich.) contaminated with Firemaster, the Hudson River (Hudson Falls, N.Y.) contaminated with Aroclor 1242, and Silver Lake (Pittsfield, Mass.) contaminated with Aroclor 1260 removed 32, 12, and 3% of the meta plus para bromines, respectively, after 32 weeks of incubation. This suggests that previous environmental exposure to PBBs enhances the debromination capability of the sediment microbial community through selection for different strains of microorganisms. The Pine River inoculum removed an average of 1.25 bromines per biphenyl molecule during a 32-week incubation period, resulting in a mixture potentially more accessible to aerobic degradation processes. No ortho bromine removal was observed. However, when Firemaster was incubated with Hudson River microorganisms that had been repeatedly transferred on a pyruvate medium amended with Aroclor 1242, 17% of the meta and para bromines were removed after 16 weeks of incubation and additional debromination products, including 2-bromobiphenyl and biphenyl, were detected. This suggests the possibility for ortho debromination, since all components of the Firemaster mixture have at least one ortho-substituted bromine.(ABSTRACT TRUNCATED AT 250 WORDS)
Rita Lochcaruso - One of the best experts on this subject based on the ideXlab platform.
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stimulation of contraction of pregnant rat uterus in vitro by non dechlorinated and microbially dechlorinated mixtures of polychlorinated biphenyls
Environmental Health Perspectives, 2001Co-Authors: Jeehyeon Bae, John F Quensen, Stephen A Boyd, Mahmoud A Mousa, Rita LochcarusoAbstract:A previous study of six polychlorinated biphenyl (PCB) congeners showed that PCBs with four or fewer chlorines and ortho substitution stimulate uterine contraction frequency in vitro, whereas congeners with a greater number of chlorines or non-ortho substitution are inactive in vitro. We tested the hypothesis that PCB mixtures stimulate uterine contractions in a manner inversely related to the degree of chlorination and the presence of chlorines in the ortho- position of the biphenyl constituents of the mixtures. Uterine strips from pregnant rats were suspended in standard muscle baths and analyzed for changes in isometric contractions in response to in vitro exposure to commercial PCB mixtures (Aroclors) and their dechlorinated products after microbial degradation. The PCB mixtures Aroclor 1242, 1248, and 1254 significantly stimulated uterine contraction frequency, and the least chlorinated mixture, Aroclor 1242, was the most potent stimulant. Microbes from Hudson River sediment dechlorinated Aroclor 1242 and Aroclor 1254 under reducing conditions to produce mixtures with an increased proportion of ortho-substituted congeners with one or two chlorine substitutions. The PCB mixtures that had undergone microbial reductive dechlorination stimulated uterine contraction frequency to a significantly greater extent than the parent mixtures. These results show that increased uterotonic activity was associated with decreased chlorination and increased ortho substitution of the biphenyl constituents of the mixtures.
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stimulation of pregnant rat uterine contraction by the polychlorinated biphenyl pcb mixture Aroclor 1242 may be mediated by arachidonic acid release through activation of phospholipase a2 enzymes
Journal of Pharmacology and Experimental Therapeutics, 1999Co-Authors: Jeehyeon Bae, Marc Petersgolden, Rita LochcarusoAbstract:The polychlorinated biphenyl (PCB) mixture Aroclor 1242 (A1242) increases frequency of contractions of pregnant rat uteri, suggesting a possible mechanism for decreased gestational age and increased spontaneous abortion in women and animals exposed to PCBs. In the present study, we hypothesized that A1242-induced stimulation of uterine contraction is mediated by arachidonic acid released by phospholipase A2 (PLA2) enzymes. Isometric uterine contraction was measured in longitudinal uterine strips isolated from gestation day 10 rat. Pretreatment of uterine strips with the PLA2 inhibitor (E)-6-(bromomethylene)tetrahydro-3-(1-naphthalenyl)-2H-pyran-2-one (HELSS) or manoalide, or an inhibitor of the G protein of PLA2, isotetrandrine, completely prevented the increase of contractile frequency induced by 50 microM A1242. However, the phospholipase C inhibitors 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate (NCDC) and neomycin were unable to block stimulation of uterine contraction by A1242. In accordance, A1242 (100 microM) did not release inositol phosphates from myo-[3H]inositol-labeled myometrial cells, whereas myometrial cells prelabeled with [3H]arachidonic acid released arachidonic acid in a concentration- and time-dependent manner after exposure to A1242 (10-100 microM). A1242 significantly stimulated arachidonic acid release in the absence of extracellular calcium, although the release was attenuated. Analysis of the eicosanoids released by A1242 indicated that only 0.83% of released [3H]arachidonic acid was metabolized to eicosanoids and 99.07% remained as free arachidonate. Uterine contraction increased in strips exposed to exogenous arachidonic acid (1-100 microM). This study suggests that A1242 stimulates contraction in pregnant rat uterus by a mechanism involving PLA2-mediated arachidonic acid release, and that arachidonic acid, rather than eicosanoids, may mediate A1242 uterotonic action in the uterus.
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stimulation of oscillatory uterine contraction by the pcb mixture Aroclor 1242 may involve increased ca2 i through voltage operated calcium channels
Toxicology and Applied Pharmacology, 1999Co-Authors: Jeehyeon Bae, Edward L Stuenkel, Rita LochcarusoAbstract:Abstract Polychlorinated biphenyls (PCBs) are persistent environmental pollutants associated with spontaneous abortion and shortened gestation length in women and animals. In previous studies, we showed that PCB mixtures and noncoplanar ortho -substituted PCB congeners increased contractions in pregnant rat uterus. In the present study, we hypothesized that the PCB mixture Aroclor 1242 (A1242) stimulates oscillatory uterine contraction in pregnant uterus by increasing intracellular calcium concentration ([Ca 2+ ] i ). Pretreatment of uterine strips with ryanodine or thapsigargin, to deplete specific intracellular calcium stores, did not prevent the increased frequency of oscillatory contraction due to 50 μM A1242, whereas thapsigargin effectively blocked carbachol-induced stimulation of uterine contraction. However, 100 μM A1242 was unable to increase contraction in the absence of extracellular calcium or in the presence of the voltage-operated L-type calcium channel blocker nifedipine. A1242 (100 μM) was observed to partially depolarize the cell membrane of myometrial cells from pregnant rats, as measured with a potential-sensitive carbocyanine dye. Changes of [Ca 2+ ] i were monitored in single myometrial cells loaded with the fluorescent calcium-sensitive probe fura-2. Cells exposed to 100 μM A1242 showed a delayed and sustained increase of [Ca 2+ ] i , and this increase was completely blocked in the absence of extracellular calcium or the presence of nifedipine. Therefore, the data suggest that depolarization of the cell membrane by A1242 enabled myometrial cells to increase [Ca 2+ ] i through activation of voltage-operated calcium channels, and the increased [Ca 2+ ] i consequently stimulated contraction of uterine smooth muscle.
Olga V Maltseva - One of the best experts on this subject based on the ideXlab platform.
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degradation of Aroclor 1242 dechlorination products in sediments by burkholderia xenovorans lb400 ohb and rhodococcus sp strain rha1 fcb
Applied and Environmental Microbiology, 2006Co-Authors: Jorge L M Rodrigues, John F Quensen, Alan C Kachel, Michael R Aiello, Olga V Maltseva, Tamara V Tsoi, James M TiedjeAbstract:Approximately 635 million kg of polychlorinated biphenyls (PCBs) were produced in the United States from 1929 to 1978, and a similar amount was manufactured in Japan, Europe, and the former USSR (19). Of the total amount, it is estimated that 31% has been released into the environment, contaminating soils and sediments (16). The high hydrophobicities of PCB molecules contribute to their accumulation in higher-trophic-level species and their long-term environmental persistence. Over the past 30 years, research on PCBs has shown that these compounds, previously thought to be recalcitrant, can be degraded by both anaerobic and aerobic bacteria. Under anaerobic conditions, anaerobic microbial consortia convert highly chlorinated congeners into less chlorinated biphenyls by reductive dechlorination, leaving the rings intact (3, 7, 30, 31). Under aerobic conditions, some microorganisms with more versatile oxidative capabilities can cleave lesser chlorinated biphenyl rings to yield chlorinated benzoates and pentanoic acid derivatives (28), which are often degradable by other bacteria. Hence, a sequential anaerobic/aerobic microbial process has the potential for the complete biodegradation of PCBs (25). Such a sequence could enable natural attenuation at aerobic-anaerobic interfaces (9) as well as be developed into a PCB bioremediation technology (37, 39). Because of their abilities to attack a wide range of PCB congeners, Burkholderia xenovorans LB400 and Rhodococcus sp. strain RHA1 are two of the more promising strains for use in the aerobic stage of a PCB biotreatment process. However, as is true of other PCB-degrading microorganisms, at best they have limited ability to grow on PCBs (29), so repeated additions (bioaugmentation) would be required for biotreatment. Both strains accumulate chlorobenzoates during PCB degradation. We reasoned that by adding genes for the dechlorination of chlorobenzoates, we could enable these strains to grow on PCBs well enough to avoid the need for repeated bioaugmentation. We have previously demonstrated this approach by separately transferring ortho (ohb) and para (fcb) chlorobenzoate-dechlorinating genes to Comamonas testosteroni VP44, obtaining constructs capable of growth on 4-chlorobenzoate (4-CBA) and 4-chlorobiphenyl (4-CB) or 2-CBA and 2-CB (17). Similarly, we transferred fcb genes to RHA1, enabling it to grow on 4-CBA and 4-CB (33). While there have been many experiments testing the ability of various aerobic bacteria to degrade PCBs, most of the work employed only one congener (27), employed a freshly applied contaminant (21), and/or was carried out under resting cell conditions (1, 26). While providing useful information, these types of experiments do not reflect the conditions under which aerobic bacteria have to perform in a biotreatment process for PCBs. PCB-contaminated sites contain a full spectrum of congeners coming from Aroclor spills, and the lengthy time they have usually had to partition into soil or sediment organic matter makes them less bioavailable than freshly spiked PCBs. Furthermore, PCB-degrading bacterial strains added to PCB-contaminated soil or sediment have to compete effectively with the indigenous soil microorganisms. These factors need to be taken into account in assessing the suitability of aerobic PCB-degrading microorganisms for use in a biotreatment process. The work reported here is an extension of our approach of adding chlorobenzoate-degrading capabilities to competent PCB-degrading microorganisms, coupled with an evaluation of the constructs obtained for use in the aerobic stage of a sequential anaerobic/aerobic biotreatment process for PCBs. We introduced ohb genes into LB400 and tested the construct first for its ability to grow on 2-chlorobenzoate and then for its ability to degrade and grow on selected PCB congeners typically formed from the microbial dechlorination of Aroclors. Finally, we simulated a sequential anaerobic/aerobic biotreatment process by dechlorinating Aroclor 1242 in anaerobic sediment slurries, establishing aerobic conditions, and adding LB400(ohb) and RHA1(fcb) together to the sediments. The constructs remained genetically stable and degraded 57% of the remaining PCBs while growing in number, successfully competing with indigenous bacteria.
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degradation of anaerobic reductive dechlorination products of Aroclor 1242 by four aerobic bacteria
Biodegradation, 1999Co-Authors: Olga V Maltseva, John F Quensen, Tamara V Tsoi, Masao Fukuda, James M TiedjeAbstract:We studied the aerobic degradation of eight PCB congeners which comprise from 70 to 85% of the anaerobic dechlorination products from Aroclor 1242, including 2-, 4-, 2,4-, 2,6-, 2,2'-, 2,4'-, 2,2', 4-, and 2,4,4'-chlorobiphenyl (CB), and the biodegradation of their mixtures designed to simulate anaerobic dechlorination profiles M and C. Strains Comamonas testosteroni VP44 and Rhodococcus erythreus NY05 preferentially oxidized a para-substituted ring, while Rhodococcus sp. RHA1, similar to well known strain Burkholderia sp. LB400, preferably attacked an ortho-chlorinated ring. Strains with ortho-directed attack extensively degraded 2,4'- and 2,4,4'-CB into 4-chlorobenzoate, while bacteria with para-directed attack transformed these congeners mostly into potentially problematic meta-cleavage products. The strains that preferentially oxidized an ortho-substituted ring readily degraded seven of the eight congeners supplied individually; only 2,6-CB was poorly degraded. Degradation of 2,2'- and 2,4,4'-CB was reduced when present in mixtures M and C. Higher efficiencies of degradation of the individual congeners and defined PCB mixtures M and C and greater production of chlorobenzoates were observed with bacteria that preferentially attack an ortho-substituted ring. PCB congeners 2,4'-, 2,2',4-, and 2,4,4'-CB can be used to easily identify bacteria with ortho-directed attack which are advantageous for use in the aerobic stage of the two-phase (anaerobic/aerobic) PCB bioremediation scheme.
Tamara V Tsoi - One of the best experts on this subject based on the ideXlab platform.
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degradation of Aroclor 1242 dechlorination products in sediments by burkholderia xenovorans lb400 ohb and rhodococcus sp strain rha1 fcb
Applied and Environmental Microbiology, 2006Co-Authors: Jorge L M Rodrigues, John F Quensen, Alan C Kachel, Michael R Aiello, Olga V Maltseva, Tamara V Tsoi, James M TiedjeAbstract:Approximately 635 million kg of polychlorinated biphenyls (PCBs) were produced in the United States from 1929 to 1978, and a similar amount was manufactured in Japan, Europe, and the former USSR (19). Of the total amount, it is estimated that 31% has been released into the environment, contaminating soils and sediments (16). The high hydrophobicities of PCB molecules contribute to their accumulation in higher-trophic-level species and their long-term environmental persistence. Over the past 30 years, research on PCBs has shown that these compounds, previously thought to be recalcitrant, can be degraded by both anaerobic and aerobic bacteria. Under anaerobic conditions, anaerobic microbial consortia convert highly chlorinated congeners into less chlorinated biphenyls by reductive dechlorination, leaving the rings intact (3, 7, 30, 31). Under aerobic conditions, some microorganisms with more versatile oxidative capabilities can cleave lesser chlorinated biphenyl rings to yield chlorinated benzoates and pentanoic acid derivatives (28), which are often degradable by other bacteria. Hence, a sequential anaerobic/aerobic microbial process has the potential for the complete biodegradation of PCBs (25). Such a sequence could enable natural attenuation at aerobic-anaerobic interfaces (9) as well as be developed into a PCB bioremediation technology (37, 39). Because of their abilities to attack a wide range of PCB congeners, Burkholderia xenovorans LB400 and Rhodococcus sp. strain RHA1 are two of the more promising strains for use in the aerobic stage of a PCB biotreatment process. However, as is true of other PCB-degrading microorganisms, at best they have limited ability to grow on PCBs (29), so repeated additions (bioaugmentation) would be required for biotreatment. Both strains accumulate chlorobenzoates during PCB degradation. We reasoned that by adding genes for the dechlorination of chlorobenzoates, we could enable these strains to grow on PCBs well enough to avoid the need for repeated bioaugmentation. We have previously demonstrated this approach by separately transferring ortho (ohb) and para (fcb) chlorobenzoate-dechlorinating genes to Comamonas testosteroni VP44, obtaining constructs capable of growth on 4-chlorobenzoate (4-CBA) and 4-chlorobiphenyl (4-CB) or 2-CBA and 2-CB (17). Similarly, we transferred fcb genes to RHA1, enabling it to grow on 4-CBA and 4-CB (33). While there have been many experiments testing the ability of various aerobic bacteria to degrade PCBs, most of the work employed only one congener (27), employed a freshly applied contaminant (21), and/or was carried out under resting cell conditions (1, 26). While providing useful information, these types of experiments do not reflect the conditions under which aerobic bacteria have to perform in a biotreatment process for PCBs. PCB-contaminated sites contain a full spectrum of congeners coming from Aroclor spills, and the lengthy time they have usually had to partition into soil or sediment organic matter makes them less bioavailable than freshly spiked PCBs. Furthermore, PCB-degrading bacterial strains added to PCB-contaminated soil or sediment have to compete effectively with the indigenous soil microorganisms. These factors need to be taken into account in assessing the suitability of aerobic PCB-degrading microorganisms for use in a biotreatment process. The work reported here is an extension of our approach of adding chlorobenzoate-degrading capabilities to competent PCB-degrading microorganisms, coupled with an evaluation of the constructs obtained for use in the aerobic stage of a sequential anaerobic/aerobic biotreatment process for PCBs. We introduced ohb genes into LB400 and tested the construct first for its ability to grow on 2-chlorobenzoate and then for its ability to degrade and grow on selected PCB congeners typically formed from the microbial dechlorination of Aroclors. Finally, we simulated a sequential anaerobic/aerobic biotreatment process by dechlorinating Aroclor 1242 in anaerobic sediment slurries, establishing aerobic conditions, and adding LB400(ohb) and RHA1(fcb) together to the sediments. The constructs remained genetically stable and degraded 57% of the remaining PCBs while growing in number, successfully competing with indigenous bacteria.
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degradation of anaerobic reductive dechlorination products of Aroclor 1242 by four aerobic bacteria
Biodegradation, 1999Co-Authors: Olga V Maltseva, John F Quensen, Tamara V Tsoi, Masao Fukuda, James M TiedjeAbstract:We studied the aerobic degradation of eight PCB congeners which comprise from 70 to 85% of the anaerobic dechlorination products from Aroclor 1242, including 2-, 4-, 2,4-, 2,6-, 2,2'-, 2,4'-, 2,2', 4-, and 2,4,4'-chlorobiphenyl (CB), and the biodegradation of their mixtures designed to simulate anaerobic dechlorination profiles M and C. Strains Comamonas testosteroni VP44 and Rhodococcus erythreus NY05 preferentially oxidized a para-substituted ring, while Rhodococcus sp. RHA1, similar to well known strain Burkholderia sp. LB400, preferably attacked an ortho-chlorinated ring. Strains with ortho-directed attack extensively degraded 2,4'- and 2,4,4'-CB into 4-chlorobenzoate, while bacteria with para-directed attack transformed these congeners mostly into potentially problematic meta-cleavage products. The strains that preferentially oxidized an ortho-substituted ring readily degraded seven of the eight congeners supplied individually; only 2,6-CB was poorly degraded. Degradation of 2,2'- and 2,4,4'-CB was reduced when present in mixtures M and C. Higher efficiencies of degradation of the individual congeners and defined PCB mixtures M and C and greater production of chlorobenzoates were observed with bacteria that preferentially attack an ortho-substituted ring. PCB congeners 2,4'-, 2,2',4-, and 2,4,4'-CB can be used to easily identify bacteria with ortho-directed attack which are advantageous for use in the aerobic stage of the two-phase (anaerobic/aerobic) PCB bioremediation scheme.