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PubMed1978

Chemical structure and biodegradability of halogenate aromatic compounds. Substituent effects on 1,2-dioxygenation of benzoic acid.

Dioxygenation of substituted benzoic acids by whole cells of 3-chlorobenzoate-utilizing Pseudomonas sp. B 13, benzoate-induced cells of Alcaligenes eutrophus B 9 and toluate-grown cells of Pseudomonas putida mt-2 was examined. Electron-attracting substituents like halogen decreased the reaction rates of benzoate 1,2-dioxygenation. Dioxygenation of substituted benzoic acids by P. putida mt-2 was mostly undisturbed by steric effects of the substituents. Good correlation resulted between the log Vrel values and the Hammett substituent constant sigma. In contrast the reaction rates of dioxygenation by Pseudomonas sp. B 13 and A. eutrophus were decreased predominantly by steric effects of substituents. A non-polar reaction mechanism of benzoate 1,2-dioxygenation is discussed. Results from inhibition studies demonstrate high stereospecificities for the 1,2-dioxygenation by Pseudomonas sp. B 13 of benzoic acids with substituents in ortho- or para-position. In the case of P. putida mt-2 steric handrance by substituents was observed only with orth-substituted benzoic acids. Stereospecificities of the benzoate 1,2-dioxygenation by Pseudomonas sp. B 13 and P. putida mt-2 are illustrated schematically.

Bacteria↗
PubMed2004

Haloalkane hydrolysis by Rhodococcus erythropolis cells: comparison of conventional aqueous phase dehalogenation and nonconventional gas phase dehalogenation.

Biofiltration of air polluted by volatile organic compounds is now recognized by the industrial and research communities as an effective and viable alternative to standard environmental technologies. Whereas many studies have focused on solid/liquid/gas biofilters, there have been fewer reports on waste air treatment using other biological processes, especially in a solid/gas biofilter. In this study, a comparison was made of the hydrolysis of halogenated compounds (such as 1-chlorobutane) by lyophilized Rhodococcus erythropolis cells in a novel solid/gas biofilter and in the aqueous phase. We first determined the culture conditions for the production of R. erythropolis cells with a strong dehalogenase activity. Four different media were studied and the amount of 1-chlorobutane was optimized. Next, we report the possibility to use R. erythropolis cells in a solid/gas biofilter in order to transform halogenated compounds in corresponding alcohols. The effect of experimental parameters (total flow into the biofilter, thermodynamic activity of the substrates, temperature, carbon chain length of halogenated substrates) on the activity and stability of lyophilized cells in the gas phase was determined. A critical water thermodynamic activity (a(w)) of 0.4 is necessary for the enzyme to become active and optimal dehalogenase activity for the lyophilized cells is obtained for an a(w) of 0.9. A temperature of reaction of 40 degrees C represents the best compromise between stability and activity. Activation energy of the reaction was determined and found equal to 59.5 KJ/mol. The pH effect on the dehalogenase activity of R. erythropolis cells was also studied in the gas phase and in the aqueous phase. It was observed that pH 9.0 provided the best activity in both systems. We observed that in the aqueous phase R. erythropolis cells were less sensitive to the variation in pH than R. erythropolis cells in the gas phase. Finally, the addition of volatile Lewis base (triethylamine) in the gaseous phase and the action of the lysozyme in order to permeabilize the cells was found to be highly beneficial to the effectiveness of the biofilter.

Air Pollutants↗
PubMed1990

Degradation of halogenated aromatic compounds.

Due to their persistence, haloaromatics are compounds of environmental concern. Aerobically, bacteria degrade these compounds by mono- or dioxygenation of the aromatic ring. The common intermediate of these reactions is (halo)catechol. Halocatechol is cleaved either intradiol (ortho-cleavage) or extradiol (meta-cleavage). In contrast to ortho-cleavage, meta-cleavage of halocatechols yields toxic metabolites. Dehalogenation may occur fortuitously during oxygenation. Specific dehalogenation of aromatic compounds is performed by hydroxylases, in which the halo-substituent is replaced by a hydroxyl group. During reductive dehalogenation, haloaromatic compounds may act as electron-acceptors. Herewith, the halosubstituent is replaced by a hydrogen atom.

Bacteria↗
PubMed2006

Stereoelectronic and inductive effects on 1H and 13C NMR chemical shifts of some cis-1,3-disubstituted cyclohexanes.

This work presents the substituent effects on the 1H and 13C NMR chemical shifts in the cis-isomer of 3-Y-cyclohexanols (Y = Cl, Br, I, CH3, N(CH3)2 and OCH3) and 3-Y-1-methoxycyclohexanes (Y = F, Cl, Br, I, CH3, N(CH3)2 and OCH3). It was observed that the H-3 chemical shift, due to the substituent alpha-effect, increases with the increase of substituent electronegativity when Y is from the second row of the periodic table of elements, (CH3 *sigma(C3--H3a) interaction energy. This interaction energy, for the halogenated compounds, decreases with an increase in size of the halogen, and this is a possible reason for the largest measured chemical shift for H-3 of the iodo-derivatives. The beta-effect of the analyzed compounds showed that the chemical shift of hydrogens at C-2 and C-4 increases with the decrease of n(Y) --> *sigma(C2-C3) and n(Y) --> *sigma(C3-C4) interaction energies, respectively, showing a behavior similar to H-3. The alpha-effect on 13C chemical shifts correlates well with substituent electronegativity, while the beta-effect is inversely related to electronegativity in halogenated compounds. NBO analysis indicated that the substituent inductive effect is the predominant effect on 13C NMR chemical shift changes for the alpha-carbon. It was also observed that C-2 and C-4 chemical shifts for compounds with N(CH3)2, OCH3 and F are more shielded in comparison to the compounds having a halogen, most probably because of the larger interaction of the lone pair of more electronegative atoms (n(N) > n(O) > n(F)) with *sigma(C2-C3), *sigma(C3-C4) and *sigma(C3-H3a) in comparison with the same type of interaction with the lone pair of the other halogens.

Carbon Isotopes↗
PubMed2001

Polychaete indicator species as a source of natural halogenated organic compounds in marine sediments.

Studies of pollutant impact on the marine environment assume that organic contaminants are anthropogenic in origin. However, many common polychaete worms and sediments contain readily detectable concentrations of brominated natural products that are often analogues of chlorinated anthropogenic contaminants. Both polychaetes and sediments are used extensively in environmental toxicology and monitoring, and the extent to which natural halometabolites may confound these studies is unknown. To characterize further the relationship among infauna, indicator species, and sedimentary halogenated organics, we examined sediments and infauna from a pristine habitat and animals maintained under laboratory culture for haloorganics using gas chromatography/mass spectrometry. Natural haloorganics are a consistent feature of pristine marine soft-bottom habitats, and their spatial and temporal variation correlates with the abundance of infauna that produce these metabolites. Abundant organohalogens are also present in the widespread polychaete indicator species Capitella sp. I and Streblospio benedicti but absent from the marine invertebrate toxicology model Neanthes arenaceodentata. Studies from the individual to the community level within the fields of ecology, toxicology, and environmental chemistry could be readily confounded by failing to consider these novel animal and habitat characteristics.

Analysis of Variance↗
PubMed2000

Mammalian class theta GST and differential susceptibility to carcinogens: a review.

Glutathione S-transferases (GSTs) are an important part of the cellular detoxification system and, perhaps, evolved to protect cells against reactive oxygen metabolites. Theta is considered the most ancient among the GSTs and theta-like GSTs are found in mammals, fish, insects, plants, unicellular algae, and bacteria. It is thought that an ancestral theta-gene underwent an early duplication before the divergence of fungi and animals and further duplications generated the variety of the other classes of GSTs (alpha, mu, phi, etc.). The comparison of the aminoacidic homologies among mammals suggests that a duplication of an ancient GST theta occurred before the speciation of mammals and resulted in the subunits GSTT1 and GSTT2. The ancestral GST theta has a dehalogenase activity towards several halogenated compounds, such as the dichloromethane. In fact, some aerobic and anaerobic methylotrophic bacteria can use these molecules as the sole carbon and energy source. The mammalian GST theta cannot sustain the growth of bacteria but still retains the dehalogenating activity. Therefore, although mammalian GST theta behaves as a scavenger towards electrophiles, such as epoxides, it acts also as metabolic activator for halogenated compounds, producing a variety of intermediates potentially dangerous for DNA and cells. For example, mice exposed to dichloromethane show a dose-dependent incidence of cancer via the GSTT1-1 pathway. Because GSTT1-1 is polymorphic in humans, with about 20% of Caucasians and 80% of Asians lacking the enzyme, the relationship between the phenotype and the incidence of cancer has been investigated extensively in order to detect GSTT1-1-associated differential susceptibility towards endogenous or exogenous carcinogens. The lack of the enzyme is related to a slightly increased risk of cancer of the bladder, gastro-intestinal tract, and for tobacco-related tumors (lung or oral cavity). More pronounced risks were found in males with the GSTT1-null genotype for brain diseases and skin basal cell carcinomas not related to sunlight exposures. Moreover, there was an increased risk of kidney and liver tumors in humans with the GSTT1-1 positive genotype following exposures to halogenated solvents. Interestingly, the liver and kidney are two organs that express the highest level of GST theta in the human body. Thus, the GSTT1-1 genotype is suspected to confer decreased or increased risk of cancer in relation to the source of exposure; in vitro studies, mostly conducted on metabolites of butadiene, confirm the protective action of GSTT1-1, whereas, thus far, experimental studies prove that the increasing risk is limited.

Amino Acid Sequence↗
PubMed1978

The development of cholecystography: the first fifty years.

Visualization of the gallbladder by x-ray was first achieved in 1923 by the intravenous introduction into the body of a halogenated compound which was excreted by the liver into the bile ducts and gallbladder [1--4]. This was the first time that visualization of an organ had been accomplished by introducing a substance into the body and obtaining a roentgenogram after the substance had been metabolized and localized primarily in one organ. Previously, visualization of an organ had been achieved only by introducing a substance opaque to the x-ray directly into the lumen and obtaining a roentgenogram to outline its inner wall. By 1925 visualization of the gallbladder had also been accomplished by the oral administration of halogenated compounds [5,6]. The drugs employed for intravenous and oral cholecystography had been synthesized specifically for that purpose based on earlier experimental work of other investigators. The following account describes in detail the experimental background of cholecystography, its origin, and its development and use during the ensuing fifty years.

Administration, Oral↗
PubMed2006

Hydroxyquinol pathway for microbial degradation of halogenated aromatic compounds.

Several peripheral metabolic pathways can be used by microorganisms to degrade toxic aromatic compounds that are known to pollute the environment. Hydroxyquinol (1,2,4-trihydroxybenzene) is one of the central intermediates in the degradative pathway of a large variety of aromatic compounds. The present review describes the microorganisms involved in the degradative pathway, the key enzymes involved in the formation and splitting of the aromatic ring of (chloro)hydroxyquinol as well as the central intermediates formed. An attempt was also made to provide some estimation for genetic basis of the hydroxyquinol pathway.

Bacteria↗
PubMed2005

Simultaneous anaerobic-aerobic biodegradation of halogenated phenolic compound under oxygen-limited conditions.

The successful application of co-immobilized aerobic-anaerobic biomass under limited aeration in wastewater treatment systems would eliminate the problems associated with the intermediates mono-chlorophenol (MCP) and di-chlorophenol(DCP) accumulations. With low initial pentachlorophenol (PCP) concentration, all PCP could be completely removed under oxygen-limited strict anaerobic conditions, and the removal efficiencies with different initial headspace oxygen percentage (IHOP) were not obviously different from each other. While at high initial PCP concentration, under strictly anaerobic conditions PCP and their intermediates were clearly higher than that under other conditions, and produced obvious accumulation, the highest PCP reduction was achieved by the system receiving 30 IHOP, oxygen-limited system also exhibited lower residual TOC concentration and lower concentration of metabolic intermediates MCP and DCP. These results suggested that under strictly anaerobic condition the reductive dechlorination of low chlorinated compounds became rate limiting in the reductive dechlorination pathway, less chlorinated compounds be more amenable to aerobic degradation, and the aerobes of outer layers could function under limited oxygen. The co-immobilized aerobic-anaerobic biomass for methanogenesis under limited-aeration for chlorophenol degradation might be an attractive and efficient alternative for the sequential anaerobic/aerobic system to achieve mineralization of a broad range of recalcitrance highly chlorinated organics and low final TOC concentrations.

Anaerobiosis↗
PubMed2006

Occurrence and expression of crdA and cprA5 encoding chloroaromatic reductive dehalogenases in Desulfitobacterium strains.

Desulfitobacterium hafniense PCP-1 (formerly frappieri PCP-1) has two reductive dehalogenases (RDases) that have been characterized. One is a membrane-associated 2,4,6-trichlorophenol RDase, which is encoded by crdA, and the other is a 3,5-dichlorophenol RDase encoded by cprA5. In this report, we determined the occurrence of these two RDase genes in seven other Desulfitobacterium strains. The presence or absence of these two RDases may explain the differences in the spectrum of halogenated compounds by these Desulfitobacterium strains. crdA gene sequences were found in all of the tested strains. It was expressed in strain PCP-1 regardless of the absence or presence of chlorophenols in the culture medium. crdA was also expressed in D. hafniense strains DCB-2 and TCE-1. cprA5 was detected only in D. hafniense strains PCP-1, TCP-A, and DCB-2. In these strains, cprA5 transcripts were detected only in the presence of chlorophenols. We also examined the expression of putative cprA RDases (cprA2, cprA3, and cprA4) that were shown to exist in the D. hafniense DCB-2 genome. RT-PCR experiments showed that cprA2, cprA3, and cprA4 were expressed in D. hafniense strains PCP-1, DCB-2, and TCP-A in the presence of chlorophenols. However, contrary to cprA5, these three genes were also expressed in the absence of halogenated compounds in the culture medium.

Bacterial Proteins↗
PubMed1989

Inactivation of laboratory animal RNA-viruses by physicochemical treatment.

Eight commonly used chemical disinfectants and physical treatments (UV irradiation and heating) were applied to both enveloped RNA viruses (Sendai virus, canine distemper virus) and unenveloped RNA viruses (Theiler's murine encephalomyelitis virus, reo virus type 3) to inactivate infectious virus particles. According to the results, alcohols (70% ethanol, 50% isopropanol), formaldehyde (2% formalin), halogen compounds (52ppm iodophor, 100ppm sodium hypochlorite), quaternary ammonium chloride (0.05% benzalkonium chloride) and 1% saponated cresol showed virucidal effects giving more than 99.95% reduction in the infectivity of virus samples of Sendai virus and canine distemper after 10 minutes exposure. There was no significant difference in the effects on the two enveloped RNA viruses. The susceptibility of unenveloped RNA viruses to chemical disinfectants and physical treatments differed greatly from the enveloped viruses. The two unenveloped viruses showed distinct resistance to 50% isopropanol, 2% formalin, 1% saponated cresol and to physical treatments (heating at 45, 56, 60 degrees C, and UV irradiation). These results indicate that using physicochemical methods to inactivate RNA viruses in laboratory animal facilities should be considered in accordance with the characteristics of the target virus. For practical purposes in disinfecting enveloped RNA viruses, 70% ethanol, 0.05% quaternary ammonium chloride and 1% saponated cresol diluted in hot water (greater than 60 degrees C) are considered as effective as UV irradiation. For unenveloped RNA viruses, halogen compounds, more than 1,000 ppm sodium hypochlorite or 260 ppm iodophor are recommended over a period of 10 minutes for disinfecting particles, although these compounds result in an oxidation problem with many metals.

Animals↗
PubMed1980

Chemical structure and biodegradability of halogenated aromatic compounds. Conversion of chlorinated muconic acids into maleoylacetic acid.

1. An enzyme for the cycloisomerization of 2- and 3-chloro-cis,cis-muconic acid was isolated from 3-chlorobenzoate-grown cells of Pseudomonas sp. B13. It was named muconate cycloisomerase II, because it could it clearly be differentiated by its Km and Vmax. values from an ordinary muconate cycloisomerase, which functioned in benzoate catabolism and exhibited low activity with the chlorinated substrates. 2-Chloro-cis,cis-muconic acid was converted into trans- and 3-chloro-cis,cis--muconic acid into cis-4-carboxymethylenebut-2-en-4-olide together with dehalogenation. 2. An enzyme was isolated from chlorobenzoate-grown cells, which converted the 4-carboxymethylenebut-2-en-4-olides into maleoylacetic acid.

Biodegradation, Environmental↗
PubMed2005

Brominated flame retardants and other organobromines in Norwegian predatory bird eggs.

A set of 62 unhatched eggs was collected from six different predatory bird species throughout Norway after incubation period was completed. They were analysed for PBDE, PBB, TBBP A and naturally occurring halogenated compounds. BDE 47, 99 and 153 were the dominating congeners, with species dependent PBDE patterns. BDE 153 was observed as the most abundant congener in eggs of peregrine falcon, golden eagle and merlin. The highest PBDE level (sum of nine congeners) was found in eggs of white-tailed sea eagle with up to 800ng/gww (median sumPBDE: 184ng/gww), followed by eggs of peregrine falcon and osprey (median sumPBDE: 155 and 105ng/gww, respectively). Golden eagle eggs showed the lowest concentration of all species (median sumPBDE: 3ng/gww). The levels in the peregrine falcon are similar to those found earlier in the Baltic region [Lindberg, P., Sellstrom, U., Haggberg, L., de Wit, C.A., 2004. Higher brominated diphenyl ethers and hexabromocyclododecane found in eggs of peregrine falcons (Falco peregrinus) breeding in Sweden. Environmental Science & Technology. 38 (1), 93-96]. The differences between species are not fully explainable, due to lack of data from the major food species. BB 101 and 153 were found in eggs of all investigated bird species. Especially in samples of white-tailed sea eagle, peregrine falcon and goshawk additional unknown penta- and hexabrominated biphenyls were detected. TBBP A was detected in all of eight eggs analysed sampled from four different bird of prey species. The naturally occurring halogenated compounds Q1, the dibromotrichloro monoterpene MHC-1, and 2,4,6-tribromoanisole (TBA) were detected in all of seven analysed samples except for one peregrine falcon egg.

Animals↗
PubMed2001

Application of the ethoxyresorufin-O-deethylase (EROD) assay to mixtures of halogenated aromatic compounds.

The ethoxyresorufin-O-deethylase (EROD) assay monitors the induction of the xenobiotic-metabolizing enzyme cytochrome P-450 (CYP) 1A1 and is a widely used biomarker for exposure of wildlife to substances that bind the aryl hydrocarbon (Ah) receptor. In this work the induction of EROD activity by single compounds and binary mixtures in primary rat hepatocytes was compared with the predictions of a kinetic model involving mixtures of inducers. The inducing agents were also examined for their ability to activate the Ah receptor to its DNA-binding form and for their ability to act as competitive inhibitors for CYP 1A1. Xenobiotics that failed to activate the Ah receptor did not induce EROD activity. Competitive inhibition for CYP 1A1 between the xenobiotic and 7-ethoxyresorufin caused EROD activity to fall at high xenobiotic concentrations. Competition for a limited number of Ah receptor sites depressed the EROD activity of a strong inducer such as 2,3,7,8-tetrachlorodibenzo-p-dioxin at high concentrations of a weak inducer. Application of the kinetic model to the example of a mixture of low concentrations of dibenzo-p-dioxins and much higher concentrations of polychlorinated biphenyls indicated that EROD assays often seriously underestimate the true potency of an environmental sample. Hence the EROD assay cannot be used for determining dioxin equivalent concentrations using the toxic equivalence factor approach.

Animals↗
PubMed2006

Brominated flame retardants and halogenated phenolic compounds in North American west coast bald eaglet (Haliaeetus leucocephalus) plasma.

We report on the identity, characterization, and spatial trends of several brominated flame retardants and hydroxylated (OH-) and methoxylated (MeO-) organohalogen contaminants in bald eagle (Haliaeetus leucocephalus) nestling plasma collected from sites along the west coast of North America. Samples were from four southwestern British Columbia (BC) locations, a reference site in northern BC (Fort St. James; FSJ), and from Santa Catalina Island, CA (SCI), an area of high DDT and PCB contamination. Mean concentrations of sigma polybrominated diphenyl ether (sigma PBDE (8 congeners monitored); 1.78-8.49 ng/g), sigma OH-polychlorinated biphenyl (sigma OH-PCB (30 congeners monitored); 0.44-0.87 ng/g), and sigma OH-PBDE (14 congeners monitored; 0.31-0.92 ng/g) were similar in eaglets from southwestern BC yet lower than for SCl and significantly higher than for FSJ. Dominant PBDE congeners were BDE47, BDE99, and BDE100, but SCl eaglets also contained low levels of higher brominated congeners. 4-OH-CB187 and 4'-OH-CB202 accounted for 65-100% of sigma OH-PCB in all BC eaglets, with 4'-OH-CB202 as well as 3'-OH-CB138 and 4-OH-CB146 dominating in SCl eaglets. Ostensibly of biogenic origin, 6'-OH-BDE49 and 6-OH-BDE47 were found in BC nestlings. Only 4'-OH-BDE49 (2.10 ng/g) was found in SCl eaglets. MeO-PBDEs and total hexabromocyclododecane (HBCD) were not found in any birds, but the polybrominated biphenyl BB101 was detected in southwestern BC samples. This study demonstrates that west coast North American bald eagles contain previously unreported organohalogens, which have the potential to impact the health and survival of these raptors.

Animals↗
PubMed2004

Automated measurement and calibration of reactive volatile halogenated organic compounds in the atmosphere.

The automated calibration and analysis of very low mixing ratios of the reactive volatile organic halocarbons CH(3)I, CHCl(3), C(2)H(5)I, 2-C(3)H(7)I, CH(2)Br(2), CH(2)ClI, CHBr(2)Cl, 1-C(3)H(7)I, CH(2)BrI, CHBr(3) and CH(2)I(2) for long term atmospheric field measurements are described. Analytes were pre-concentrated from 3 l of air onto an adsorbent trap cooled to -10 [degree]C using Peltier plates, and rapidly transferred to a gas chromatograph (GC) by resistive heating. A two stage Carboxen 1016/Carbotrap C adsorbent trap allowed good analyte recovery and rapid desorption without the need for post-desorption cryofocussing. Halocarbons were detected using a mass spectrometer (MS) in selective ion mode. Detection limits were between 0.02 and 0.12 pptv (parts per trillion by volume) for approximately hourly samples of CHCl(3), CH(3)I, C(2)H(5)I, 1-C(3)H(7)I, 2-C(3)H(7)I, CH(2)ClI, CH(2)Br(2), CHBr(2)Cl, CH(2)BrI, CHBr(3) and CH(2)I(2) with a precision of 3-8%. A novel calibration system was constructed which utilised fixed volume (50 [micro sign]l) injections of the output of thermostatted permeation tubes into a stream of nitrogen gas in order to dilute parts per million by volume (ppmv) mixing ratios into pptv. The calibration was completely automated, allowing multi-point calibrations during routine operation. The overall accuracy of the measurements is estimated to be +/-15%. The instrument was used continuously for automated atmospheric measurements during a 4-month research cruise from Germany to Antarctica, and a 6 week field campaign at Mace Head, Ireland. The results for CHCl(3) during the latter campaign were within 13% of measurements made by a GC-MS operating continuously at the site within the long term Advanced Global Atmospherics Gases Experiment.

Air Pollutants↗