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PubMed1991

Quantitative structure-activity relationships for chemical toxicity to environmental bacteria.

Quantitative structure-activity relationships (QSARs) were developed for nonreactive chemical toxicity to each of four groups of bacteria of importance in environmental engineering: aerobic heterotrophs, methanogens, Nitrosomonas, and Microtox. The QSARs were based on chemicals covering a range of structures and including important environmental pollutants (i.e., chlorinated and other substituted benzenes, phenols, and aliphatic hydrocarbons). QSARs were developed for each chemical class and for combinations of chemical classes. Three QSAR methods (groups of chemical describing parameters) were evaluated for their accuracy and ease of use: log P, linear solvation energy relationships (LSER), and molecular connectivity. Successful QSARs were found for each group of bacteria and by each method, with correlation coefficients (adjusted r2) between 0.79 and 0.95. LSER QSARs incorporated the widest range of chemicals with the greatest accuracy. Log P and molecular connectivity QSARs are easier to use because their parameters are readily available. Outliers from the QSARs likely due to reactive toxicity included acryls, low pKa compounds, and aldehydes. Nitro compounds and chlorinated aliphatic hydrocarbons and alcohols showed enhanced toxicity to the methanogens only. Chemicals with low IC50 concentrations (log IC50 mumol/liter less than 1.5) were often outliers for Nitrosomonas. QSARs were validated statistically and with literature data. A suggested method is provided for use of the QSARs.

Bacteria↗
PubMed1994

Aerobic mineralization of trichloroethylene, vinyl chloride, and aromatic compounds by rhodococcus species.

Two Rhodococcus strains which were isolated from a trichloroethylene (TCE)-degrading bacterial mixture and Rhodococcus rhodochrous ATCC 21197 mineralized vinyl chloride (VC) and TCE. Greater than 99.9% of a 1-mg/liter concentration of VC was degraded by cell suspensions. [1,2-C]VC was degraded by cell suspensions, with the production of greater than 66% CO(2) and 20% C-aqueous phase products and incorporation of 10% of the C into the biomass. Cultures that utilized propane as a substrate were able to mineralize greater than 28% of [1,2-C]TCE to CO(2), with approximately 40% appearing in C-aqueous phase products and another 10% of C incorporated into the biomass. VC degradation was oxygen dependent and occurred at a pH range of 5 to 10 and temperatures of 4 to 35 degrees C. Cell suspensions degraded up to 5 mg of TCE per liter and up to 40 mg of VC per liter. Propane competitively inhibited TCE degradation. Resting cell suspensions also degraded other chlorinated aliphatic hydrocarbons, such as chloroform, 1,1-dichloroethylene, and 1,1,1-trichloroethane. The isolates degraded a mixture of aromatic and chlorinated aliphatic solvents and utilized benzene, toluene, sodium benzoate, naphthalene, biphenyl, and n-alkanes ranging in size from propane to hexadecane as carbon and energy sources. The environmental isolates appeared more catabolically versatile than R. rhodochrous ATCC 21197. The data report that environmental isolates of Rhodococcus species and R. rhodochrous ATCC 21197 have the potential to degrade TCE and VC in addition to a variety of aromatic and chlorinated aliphatic compounds either individually or in mixtures.

Journal Article↗
PubMed2000

Prediction of gas chromatographic retention indices of polychlorinated dibenzothiophenes on non-polar columns.

Polychlorodibenzothiophenes (PCDTs) have been found in several kinds of environmental samples. The lack of reference compounds has meant that very little is known about their gas chromatographic behavior. Here we discuss the retention of 19 authentic PCDTs and their sulfones on the widely used gas chromatographic stationary phases DB-5 and DB-5ms. The retention order is different from that of the polychlorodibenzofurans. The data generated allowed us to carry out a multiple linear regression to generate parameters for predicting the retention indices of unknown congeners based only on their structural features.

Chlorine Compounds↗
PubMed2006

Implications of sequential use of UV and ozone for drinking water quality.

The formation of bromate levels exceeding the drinking water standard of 10 microg L-1 may impose the reduction of ozone doses used in the treatment of drinking water. This paper illustrates the procedure of evaluating the use of reduced ozone doses while implementing an additional UV disinfection step for an actual drinking water treatment plant. Ozonation was performed at low ozone doses in bench-scale experiments with a pretreated river water from the Paris area (France). At the low ozone dose of 0.5 mg L-1, bromate formation could be kept below 0.4 microg L-1, while inactivation of vegetative bacteria and UV-resistant viruses was calculated to exceed 5 log units, and a substantial decoloration (31% of the absorption at lambda=254 nm) was achieved. Based on the measured transient ozone and OH radical concentrations, the oxidation of micropollutants was calculated. Fast reacting micropollutants containing phenol, amine or double bond moieties, such as sulfamethoxazole, diclofenac and 17-alpha-ethinylestradiol, were completely oxidized. Slow-reacting synthetic micropollutants, e.g., atrazine, iopromide and methyl tertiary butyl ether (MTBE), were oxidized by only 20%, 20% and 10%, respectively, and the taste and odor compounds 2-methylisoborneol (MIB) and geosmin by 40% and 50%, respectively. The addition of an UV treatment step to the existing treatment train, which should guarantee disinfection of ozone-resistant pathogenic microorganisms, including Cryptosporidium parvum oocysts, has negligible effects on water matrix components but may induce significant transformation of micropollutants. Overall, the combination of ozonation at reduced doses and UV treatment leads to an improved water quality with regard to disinfection, oxidation of micropollutants and minimization of bromate.

Bromates↗
PubMed2004

Endocrine disrupters in the aquatic environment: the Austrian approach--ARCEM.

A consortium of Austrian scientists (ARCEM) carried out a multidisciplinary environmental study on Austrian surface and ground waters including chemical monitoring, bioindication, risk assessment and risk management for selected endocrine disrupters: 17beta-estradiol, estriol, estrone, 17alpha-ethinylestradiol, 4-nonylphenol, 4-nonylphenol ethoxylates (4-NP1EO, 4-NP2EO) and their degradation products, ocytlphenol, ocytlphenol ethoxylates (OP1EO, OP2EO) as well as bisphenol A. To obtain data representative for Austria, a material flow analysis served to select relevant compounds and water samples were collected monthly over one year at those sites routinely used in Austrian water quality control. The following results were obtained and conclusions drawn: 1. Chemical monitoring: As compared to other countries, relatively low levels of pollution with endocrine disrupters were detected. 2. Bioindication: In the surface waters under study, male fish showed significant signs of feminization and demasculinization (increased production of the egg-yolk protein and histological changes of the gonads. 3. Risk assessment: For humans, exposure via either drinking water abstraction (ground water) or fish consumption was considered. The exposure levels of the compounds under study were below those considered to result in human health risks. Likewise, for bisphenol A and octylphenols, there was no indication for risk posed upon the aquatic environment (fish). However, nonylphenol or 17alpha-ethinylestradiol exposure along with results of bioindication (2) suggest a borderline estrogenic activity in a considerable number of surface waters. Consequently the emissions of these substances into the surface waters affected have to be reduced. 4. Risk management: Waste water treatment experiments revealed a positive correlation between the removal rate of endocrine disrupters from the waste water and the sludge retention time in the treatment plants. These substances are removed to a higher extend at low loaded plants designed for nutrient removal than at plants that remove carbon and/or employ nitrification only. As to drinking water treatment, chlorine dioxide and ozone were found to eliminate all investigated substances, except nonylphenol ethoxylates. (For the complete study see: www.arcem.at)

Animals↗
PubMed2003

Evaluation of bacterial aerotaxis for its potential use in detecting the toxicity of chemicals to microorganisms.

Bacterial aerotaxis (the movement of a cell toward oxygen) was evaluated for its potential use in detecting the toxicity of chemicals to microorganisms. The level of toxicity was determined by the concentration of test chemicals resulting in a 50% inhibition of aerotaxis of Pseudomonas aeruginosa PAO1 after 40 min of exposure. The aerotactic responses of P. aeruginosa were measured by using chemotaxis well chambers. Each clear acrylic chamber had a lower and upper well separated by a polycarbonate filter with a uniform pore size of 8.0 microm. To automatically detect bacterial cells that crossed the filter in response to a gradient of oxygen, P. aeruginosa PAO1 was marked with green fluorescent protein (GFP), and the GFP fluorescence intensity in the upper well was continuously monitored by using a fluorescence spectrometer. By using this technique, volatile chlorinated aliphatic compounds, including trichloroethylene (TCE), trichloroethane, and tetrachloroethylene, were found to be inhibitory to bacterial aerotaxis, suggesting their possible toxicity to microorganisms. We also examined more than 20 potential toxicants for their ability to inhibit the aerotaxis of P. aeruginosa. Based on these experimental results, we concluded that bacterial aerotaxis has potential for use as a fast and reliable indicator in assessing the toxicity of chemicals to microorganisms.

Biosensing Techniques↗
PubMed1991

Treatment of Trichophyton mentagrophytes infection in rabbits.

Copper sulfate and a metastabilized chlorous acid/chlorine dioxide (MECA) compound were evaluated for efficacy in treating Trichophyton mentagrophytes infection in rabbits. Forty rabbits naturally infected with T mentagrophytes were allotted to 5 treatment groups: nontreated control, sham dip, 1% copper sulfate dip, MECA dip, and MECA spray. Results of lesion culture, regression of gross lesions, and histopathologic findings were documented. Copper sulfate and MECA were effective in treating clinical dermatophytosis and in decreasing T mentagrophytes carrier status in rabbits.

Administration, Topical↗
PubMed1995

Effects of local and distant contaminant sources: polychlorinated biphenyls and other organochlorines in bottom-dwelling animals from an Arctic estuary.

Elevated concentrations of organochlorines in the tissues of large marine predators in the Canadian Arctic are well documented. This paper presents some of the first data on the composition and distribution of chlorinated organic compounds in some arctic coastal animals found at lower levels of the marine food chain. Organisms include bottom-dwelling invertebrates: clams (Mya truncata), mussels (Mytilus edulis), sea urchins (Strongylocentrotus droebachiensis) and fish: sculpins (Myoxocephalus quadricornis). The majority of samples were collected in the vicinity of Cambridge Bay, Northwest Territories (NWT), Canada; however, samples were also collected near another inhabited area (Hall Beach, NWT) and at a reference site (Wellington Bay, NWT). PCBs and other organochlorines typically originate in more industrialized parts of the northern hemisphere, enter the Arctic, and are subsequently biomagnified. In this study, differences in the PCB congener compositions and concentrations, as well as the relative concentrations of a larger suite of organochlorines in biota, allowed the discrimination between local and distant PCB sources. Terrestrial runoff from southern Victoria Island, NWT, has resulted in localized elevation of PCBs and chlorinated pesticides in marine sediment and bottom-dwelling animals. The major inputs of PCBs to coastal waters within Cambridge Bay were derived from local sources (the hamlet dump and DEW Line site). In addition, transport from more distant sources via riverine input accounts for locally elevated concentrations of other organochlorines in upper Cambridge Bay. This process may also account for concentrations of all measured organochlorines that are higher in Wellington Bay than in Queen Maud Gulf. The high PCB concentrations in the whole tissue (excluding liver) or livers of four-horned sculpins in Cambridge Bay (up to 220 ng/g and 1950 ng/g, respectively) and, to a lesser extent, Wellington Bay (3.8 ng/g and 47 ng/g, respectively) reflect a strong tendency for biomagnification of PCBs in coastal benthic communities.

Animals↗
PubMed1980

Genetic effects of chlorinated anilines and azobenzenes on Salmonella typhimurium.

The mutagenicity of 19 herbicide-derived chlorinated azobenzenes and structurally related chlorinated anilines and nitrobenzenes was assayed towards several strains of S. typhimurium, using the plate incorporation method and the fluctuation test, in the presence or in the absence of liver post-mitochondrial fractions, in aerobic and anerobic conditions. Positive results were obtained with 4,4'-dichloroazobenzene, 4,4'-dichloroazoxybene, 3,4-dichloronitrobenzene and, to a much lesser extent, with 3,4,3',4'-tetrachloroazobenzene. No mutagenic effect was observed with 2,3,7,8-tetrachlorodibenzo-p-dioxin in any condition.

Aerobiosis↗
PubMed2001

Selective trapping of organochlorine compounds in mountain lakes of temperate areas.

The study of fish concentrations and sediment inventories in 19 European high mountain lakes (40-67 degrees N) shows that a fraction of organochlorine compounds (OCs), the less volatile compounds (LVC; subcooled liquid vapor pressure < or = 10(-2.5) Pa), are trapped in the higher locations. This general trend is not significantly influenced by possible local sources. Compound distribution is related to average air temperatures. The phase-change pseudoenthalpies calculated from the sediment inventories closely match the summed theoretical volatilization and dissolution enthalpies. This fractionation effect is responsible for the accumulation of high concentrations of the LVC, the more persistent and toxic according to literature data, in organisms inhabiting sites far from the locations of synthesis or use.

Air Pollutants↗
PubMed2005

Characterization of the PCB substrate range of microbial dechlorination process LP.

We have characterized the substrate range of Process LP, a PCB dechlorination activity mediated by anaerobic bacteria, in Housatonic River sediment (Lenox, MA). Process LP has the rare ability to remove unflanked para chlorines from polychlorinated biphenyls (PCBs). We used 2,6-difluoro-4-chlorobiphenyl (DFCB) to activate Process LP in anoxic sediment microcosms and tested its ability to dechlorinate 34 potential PCB substrates, all of which are significant components of PCB mixtures found in contaminated sediments. We used gas chromatography-mass spectrometry to monitor the dechlorination of DFCB and PCBs and the appearance of products. The preferred substrates for Process LP were PCB congeners in which the target para chlorines were flanked by meta chlorines, such as those having 3,4- and 2,4,5-chlorophenyl rings. The unflanked para chlorines on PCBs with 2,4-, 2,4,6-, and sometimes 4-chlorophenyl rings, were also substrates. Furthermore, the data revealed that Process LP can also meta-dechlorinate 2,3-, 2,3,4-, and 2,3,5-chlorophenyl groups on some congeners. A single ortho chlorine on the unattacked ring generally enhanced dechlorination activity, but the presence of 3 or 4 ortho chlorines or a 4-chlorophenyl group decreased the dechlorination efficiency. PCBs with 2,4-, 2,4,6-, 2,3-, and 2,3,5-chlorophenyl rings are often terminal dechlorination products of other microbial dechlorination activities. Since these PCBs are substrates for Process LP, this dechlorination activity works especially well in tandem with other dechlorination activities and further reduces the toxicity and persistence of PCBs. The data presented here will facilitate the construction of accurate models to interpret in situ PCB dechlorination and predict PCB fate.

Anaerobiosis↗
PubMed1999

Effects of polydiallyldimethyl ammonium chloride coagulant on formation of chlorinated by products in drinking water.

The objectives of this research work was to evaluate the reduction of THM precursors by cationic p-DADMAC and determine the correlations between the chlorine demand and trihalomethane formation in the presence of electrolyte solutions and ambient light. The chlorine demand was found to be significantly reduced provided that the H2SO4 electrolyte was fed to the sample solutions. The amount of CHCl3 formation was also decreased when the Na2SO4 electrolyte was introduced in spite of the levels of light intensity. The p-DADMAC can not only effectively remove the turbidity but also reduce the formation of CHCl3. The optimum dosage of p-DADMAC for reducing the turbidity, TOC and CHCl3 in the humic acid and source water samples was determined and depended upon the nature of organics.

Allyl Compounds↗
PubMed2001

Effects of 2,4-dichlorophenoxy acetic acid dimethyl amine salt on dental hard tissue formation in rats.

2,4-Dichlorophenoxy acetic acid dimethyl amine salt (2,4-D DMA), as one of the phenoxy acids, is used as a herbicide mainly against broad-leaf weeds in cereal crops, sugar cane, and on turf, pasture, and non-crop land. Some formulations of 2,4-D may be contaminated with dioxins. Recently, it has been shown that chlorinated organic compounds, dioxins, and furans are present in mother's milk and may cause developmental defects in children's teeth. Therefore, we aimed to evaluate the effects of 2,4-D DMA on odontogenesis in rats. 2,4-D DMA was given orally combined with rat food to pregnant albino rats. Each group consisted of two pregnant rats and, 0 (control, group A), 25 ppm (group B), 50 ppm (group C), and 100 ppm (group D) 2,4-D DMA was given to each pregnant rat as daily intake. 2,4-D DMA affected young rat's dental development and dose-related findings were found in experimental groups. The odontoblast layer was irregular and globular dentin formation was present in Groups B, C, and D but not in the control group. Thickness of enamel decreased in Groups C and D. The results of the study have shown that 2,4-D DMA could disturb dental development in rats even in relatively low doses. It is concluded that environmental contaminants such as chlorinated organic pesticides may play an important role in infant's dental development when taken via mother's milk.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1992

Induction of prophage lambda by chlorinated organics: detection of some single-species/single-site carcinogens.

Twenty-eight chlorinated organic compounds were evaluated for their ability to induce DNA damage using the Microscreen prophage-induction assay in Escherichia coli. Comparison of the performance characteristics of the prophage-induction and Salmonella assays to rodent carcinogenicity assays showed that the prophage-induction assay had a somewhat higher specificity than did the Salmonella assay (70% vs. 50%); sensitivity, concordance, and positive and negative predictivity were similar for the two microbial assays. The Microscreen prophage-induction assay failed to detect eight carcinogens, perhaps due to toxicity or other unknown factors; five of these eight carcinogens were detected by the Salmonella assay. However, the prophage-induction assay did detect six carcinogens that were not detected by the Salmonella assay, and five of these were single-species, single-site carcinogens, mostly mouse liver carcinogens. Some of these carcinogens, such as the chloroethanes, produce free radicals, which may be the basis for their carcinogenicity and ability to induce prophage. The prophage-induction (or other SOS) assay may be useful in identifying some genotoxic chlorinated carcinogens that induce DNA damage that does not revert the standard Salmonella tester strains.

Animals↗
PubMed2006

Comparison of 2-chlorobenzoic acid biodegradation in a membrane bioreactor by B. cepacia and B. cepacia bearing the bacterial hemoglobin gene.

Degradation of 2-chlorobenzoic acid (2-CBA), a model recalcitrant chlorinated organic compound, by pure cultures of Burkholderia cepacia strain DNT with (transformed B. cepacia) and without (untransformed B. cepacia) the bacterial hemoglobin (Vitreoscilla hemoglobin, VHb) gene, vgb, was investigated in parallel membrane bioreactors (MBRs). This was done aseptically to prevent contamination during the operation of the MBRs. The objective was to determine whether the degradation of 2-CBA by cometabolism, using acetate as a primary carbon source, under hypoxic conditions might be enhanced for vgb-bearing cells in MBRs. The 2-CBA removal efficiency of transformed B. cepacia (97-99%) was slightly higher than that of untransformed B. cepacia (95-99%) at all stages. The average amount of chloride released from 2-CBA by transformed cells was also higher than for untransformed cells, 92-96% compared to 64-84% of the maximum theoretical amount, the exact value depending on the operating conditions. These results indicate that 2-CBA degradation/transformation is not accompanied by the stoichiometric release of chloride for the untransformed strain. The difference between percentages of 2-CBA removal and chloride release by untransformed cells was attributed to persistence, under hypoxic conditions, of the 2-CBA chlorine atom in 2-CBA metabolites. Growth of transformed cells was also significantly enhanced under hypoxic conditions compared to untransformed cells. For varying media compositions, the transformed cells reached higher cell densities (3.2-5.4 g/L) relative to untransformed cells (2.8-4.7 g/L) at food to microorganism ratios ranging from 0.44-0.59 to 0.38-0.49 g COD/g biomass-d The observed yields thus ranged from 0.16-0.20 and 0.15-0.18 g TSS/g COD for untransformed and transformed cells, respectively. The value of the yield depended on medium composition. The MBR system using vgb-containing B. cepacia maintained a high biomass concentration without oxygen limitations and provided cell-free effluent. Hence, it may be useful for treating high volumes of water contaminated with low levels of recalcitrant organics.

Bacterial Proteins↗
PubMed2001

Trends of organochlorine compounds in Finnish inland waters. Results of mussel incubation monitoring 1984-1998.

Caged common lake mussels (Anodonta piscinalis) have been used in the monitoring of organochlorine compounds in pulp and paper mill recipient watercourses of Finland annually from 1984 to 1998. Statistically significant decreasing trends of chlorophenols and chloroguaiacols originating from chlorobleaching were observed in all recipients in parallel with the decreasing discharges from the mills. Metabolites of chlorophenols, chloroanisoles and chloroveratroles had no or slightly increasing trends. Elevated PCB concentrations were measured in four watercourses. In two areas, PCBs were found to be significantly increasing, in two other cases they showed no trend. A mill producing recycled paper was apparently responsible for an increase of PCBs and DDE in recipient watercourses. Overall decreases were observed for other chlorohydrocarbons except for DDT. Material flows of chlorohydrocarbons were positively correlated with waterflows (Q) in some cases.

Animals↗
PubMed2004

Regulation of anaerobic dehalorespiration by the transcriptional activator CprK.

Desulfomonile, Desulfitobacterium, and Dehalobacter are anaerobic microbes that can derive energy from the reductive dehalogenation of chlorinated organic compounds, many of which are environmental pollutants. There is very little information about how anaerobic dehalorespiration is regulated. An open reading frame within the Desulfitobacterium dehalogenans chlorophenol reductase (cpr) gene cluster (cprK) was proposed to be a transcriptional regulatory protein (Smidt, H., van Leest, M., van der Oost, J., and deVos, W. M. (2000) J. Bacteriol. 182, 5683-5691). We have cloned, actively overexpressed in Escherichia coli, and purified to homogeneity the D. dehalogenans CprK. The results of electrophoretic mobility shift assays, DNA footprinting studies, and promoter-lac fusion experiments indicate that CprK is a transcriptional activator of the cpr gene cluster. CprK binds 3-chloro-4-hydroxyphenylacetate (CHPA) with high affinity (K(d) = 3.5 mum, determined by isothermal titration calorimetry), which promotes its specific interaction with a DNA sequence (TTAAT-N4-ACTAA) located upstream of the -35 and -10 promoter regions of several cpr genes and activates transcription of these genes. Binding to the upstream "box" sequence increases the affinity of CprK for CHPA by approximately 10-fold (K(d) = 0.4 mum, determined by electrophoretic mobility shift assays). Chlorophenylacetate, which lacks the ortho-hydroxy group, and hydroxyphenylacetate, lacking the chlorine group, do not activate transcription or promote DNA binding, even at millimolar concentrations, at least 1000-fold higher than the K(d) value for CHPA. Lacking metals, CprK is oxygen-sensitive. Oxidation by diamide, which converts thiols to the disulfide, inactivates CprK, and reduction of the oxidized protein by dithiothreitol fully restores DNA binding, indicating that CprK is redox-regulated and is active only when reduced. This is the first reported characterization of a transcriptional regulator of anaerobic dehalorespiration.

Base Sequence↗
PubMedDate not supplied

Ranking of phenols for abiotic oxidation in aqueous environment: a QSPR approach.

The limited availability and variability of data related to the overall degradation of compounds in the environment is a very relevant issue in studies related to environmental fate and chemical behavior. The studied phenol data set consists of reaction rate constants of different oxidation reactions in surface waters, available either experimentally or, to fill the data gap, from our QSAR models reported herein. A PCA (Principal Component Analysis) model based on these oxidative degradations has been proposed to evaluate the degradability of chemicals. The score of the first Principal Component is modelled by theoretical molecular descriptors to obtain a multiple linear regression (MLR) model with high predictive power, both internally and externally validated. This modeling approach allows a fast and preliminary ranking of phenols according to their tendency to be degraded by oxidants in water, starting only from knowledge of their molecular structure.

Chlorine Compounds↗