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PubMed2001

Water disinfection for international and wilderness travelers.

Acquisition of waterborne disease is a substantial risk for international travelers to countries with inadequate sanitation facilities. It also poses smaller but still significant risks for wilderness travelers who rely on surface water in developed countries with low rates of diarrheal illness, such as the United States. This article reviews the etiology and risks associated with waterborne disease that might be encountered by both types of travelers. It also summarizes--and makes recommendations for--the various water-treatment methods available to travelers for reducing their risk of contracting waterborne disease.

Alum Compounds↗
PubMed1994

Studies on intrachromosomal recombination in SP5/V79 Chinese hamster cells upon exposure to different agents related to carcinogenesis.

In the present study 34 agents, related to carcinogenesis in different ways, were investigated with respect to their recombinogenic activity in mammalian cells. The induction of intrachromosomal recombination was studied using the spontaneous mutant clone SP5 derived from V79 Chinese hamster cells, which exhibits a duplication of exon 2 and its flanking regions in the hprt gene, which was found to be inserted between the two EcoR1 sites of intron 1. Earlier studies on the removal of this insertion fragment in the SP5 clone indicated that such loss involved intrachromosomal recombination and was detectable by using a reversion mutation assay. The categories of agents investigated here included monofunctional alkylating agents, polyaromatic hydrocarbons giving rise to bulky adducts, chlorinated compounds giving small cyclic adducts, intercalating agents, DNA cross-linkers, UV and ionizing radiation, inhibitors of DNA synthesis and topoisomerases, DNA bases and base analogues, radical formers and tumour promotors. Statistically significant enhancements in the frequency of reversion in SP5 cells were observed after treatment with aflatoxin B1, 9-aminoacridine, benzo[a]-pyrene-7,8-dihydrodiol, benzo[a]pyrene-7,8-diol-9,10-epoxide, camptothecin, dimethylbenzanthracene, dimethyl-nitrosamine, ethidium bromide, ethylmethanesulfonate, N-ethyl-N'-nitrosourea, fluorodeoxyuridine, ICR 191, N-methyl-N'-nitrosoguanidine, mitomycin C and UV irradiation. Only slight inducing effects were indicated in the case of methylmethanesulfonate, N-methyl-N'-nitrosourea and gamma irradiation, although not statistically significant. Negative results were found after treatment with 3-amino-benzamide, 5-azacytidine, bleomycin, 5-bromodeoxyuridine, 1,2-dichloroethane, ethylene oxide, etoposide, formaldehyde, hydrogen peroxide, methotrexate, propylene oxide, quercitin, sodium azide, 12-O-tetradecanoylphorbol-13-acetate, thymidine and a complex mixture consisting of a cigarette smoke condensate. Our results on chemically or physically induced recombinogenic effects in the endogenous SP5 hprt gene are in agreement with data obtained in non-endogenous gene systems based on transgenic cell lines containing integrates of tandem mutated tk or hygromycin resistance genes, but not completely consistent with findings on integrates based on the neo genes. This suggests that many factors influence the recombination process, including a difference in the mechanisms underlying inter- and intrachromosomal recombination. Consequently, the endogenous SP5/V79 system is suggested to be more representative than integrated systems for investigating induction of recombination, as well as for mechanistic studies of recombination at the molecular level, e.g. intrachromosomal recombination.

Animals↗
PubMed2002

Temperature effect on peak width and column efficiency in subcritical water chromatography.

Subcritical water has been recently employed as the mobile phase to eliminate the use of organic solvents in reversed-phase liquid chromatography. Although the influence of temperature on retention in subcritical water chromatography has been reported, the temperature effect on peak width and column efficiency has not yet been quantitatively studied. In this work, several polar and chlorinated compounds are separated using pure subcritical water on Zorbax RX-C8, PRP-1 (polystyrene-divinylbenzene), Hypersil ODS, and ZirChrom-polybutadiene columns. Isothermal separations are performed at temperatures ranging from 60 degrees C to 160 degrees C. The retention time and peak width of analytes are reduced with increasing temperature. However, the column efficiency is either improved or almost unchanged with the increasing temperature in the low-temperature range (lower than the 100 degrees C to 120 degrees C range), but it is decreased when temperature is further raised in the high-temperature range (higher than the 100 degrees C to 120 degrees C range). Therefore, a maximum in column efficiency is obtained at temperatures within the 100 degrees C to 120 degrees C range in most cases.

Journal Article↗
PubMed1999

The postantibiotic effect of N-chlorotaurine on Staphylococcus aureus. Application in the mouse peritonitis model.

This study was designed to investigate the delay of regrowth (postantibiotic effect) in the presence of N-chlorotaurine (NCT), an endogenous active N-chlorine compound, of Staphylococcus aureus, strain Smith diffuse. The low reactivity of NCT enabled clear temporal separation of the postantibiotic and killing effect to be defined. Delay of regrowth proved to be dependent both on concentration of NCT, and incubation time. The maximum delay was 3 h. Using the model of lethal staphylococcal peritonitis in mice, in-vivo delay of regrowth of bacteria pretreated with N-chlorotaurine could be demonstrated to correlate with survival. It is concluded that the postantibiotic effect of N-chlorotaurine could be an important factor on decreasing virulence of bacteria. This effect was observed after relatively short incubation times.

Analysis of Variance↗
PubMed1987

Performance of short-term tests for detection of human carcinogens.

The performance of short-term tests for detection of carcinogens has been validated by several investigators and international collaborative programmes. A large number of chemicals have been tested by the Salmonella/microsome assay and high values of sensitivity and specificity, often greater than 70%, were reported. For 71 human carcinogens classified in Groups 1, 2A and 2B by the International Agency for Research on Cancer (IARC), the Salmonella/microsome test showed a sensitivity of 62.1%: 36 were positive out of 58 chemicals tested. Similar or rather higher values were obtained with Escherichia coli mutation assay (72.0%, 18/25), mutation assays in fungi (78.9%, 30/38), mutation assays in insects (65.7%, 23/35), and assays measuring DNA damage in prokaryotes (80.5%, 33/41). In assays using mammalian cells, tests on chromosomal anomaly showed a relatively high sensitivity: 61.7% (29/47) in chromosomal structural aberration assays and 80.6% (25/31) in sister chromatid exchange (SCE) assays. Comparable values were also obtained in mutation assays of mammalian cells (73.0%, 27/37) and cell transformation assays (87.5%, 21/24). Results of monitoring of exposed populations did not necessarily show a high sensitivity to human carcinogens (44.4%, 12/27). Human carcinogen data were further analysed in order to find a combination of tests which may increase the predictive value. Among human carcinogens, 17 chemicals are not mutagenic in the Salmonella/microsome assay. Although 9 of 17 chemicals (asbestos, hormones, chlorinated compounds and 1,4-dioxane) were not positive in any short-term assays, some gave positive results in a variety of assays, e.g. arsenic and benzene were positive in assays of chromosomal anomaly in mammalian cells in vitro. Combinations of the Salmonella/microsome assay with certain tests using mammalian cells were found to increase the sensitivity significantly. Chromosomal anomaly assays of mammalian cells in vitro seem to be most relevant for detection of human carcinogens when used in combination with the Salmonella/microsome assay.

Animals↗
PubMed1996

Emergency response to environmental toxic incidents: the role of the occupational physician.

A survey of accidental environmental releases of hazardous chemicals conducted by the Agency for Toxic Substances and Disease Registry indicates that fixed facility events accounted for 77% of the episodes whereas 23% of the releases were related to transportation activities, such as loading or unloading materials. In nearly all the events (88%) only one chemical was released. Volatile organic compounds, chlorine, herbicides, acids and ammonia were the most common substances involved. In nearly one out of six reported events, an injury occurred. To prepare for emergencies associated with the accidental release of hazardous materials, the federal government, industry and professional organizations including the medical community have all been involved. In the United States, the Superfund Amendment Reauthorization Act (SARA) Title III passed in 1986 addresses the need to establish local emergency planning committees, to report and collect data, and a number of other matters. Professional societies, including the Joint Commission for the Accreditation of Health Care Organizations, the American College of Occupational and Environmental Medicine (ACOEM), and the American Industrial Hygiene Association, have all attempted to ensure proper education and training of those professionals called to assist in such emergencies. The occupational physician can assume numerous roles in the challenge related to emergency response, by becoming familiar with computerized information available to promptly determine the type of hazard released and its appropriate antidote, advising on the proper personal protective equipment, awareness of secondary contamination and participation on local emergency planning committees among many others. Emergency release of hazardous materials continues to occur with a frequency in the United States that deserves active vigilance and planning.

Accidents, Occupational↗
PubMed1991

Stimulation by gonococci of chloride ion uptake in human leucocytes in relation to other properties of phagocytosis.

Human polymorphonuclear leucocytes (PMNL) underwent several changes in response to challenge with Neisseria gonorrhoeae, namely (1) an increase in oxygen uptake, (2) changes in membrane electrical properties, and (3) increased transport of chloride ions (Cl-) across the membrane. Mean oxygen consumption and Cl- uptake by PMNL were stimulated by both pilate (P+) and non-pilate (P-) gonococci, although the levels were much reduced in the presence of P+ organisms. P+ gonococci also initiated low levels of polarisation or depolarisation in contrast with P- cells, which caused hyperpolarisation followed by depolarisation in the PMNL. Most of the strains showed these patterns. High performance liquid chromatography of extracts of unstimulated PMNL and of PMNL challenged with gonococci confirmed production of hypochlorous acid (HOCl) in the leucocyte. Furthermore, addition of radiolabelled Cl- to the PMNLs showed that some of the Cl- taken up by the cells in response to gonococcal challenge was incorporated into the HOCl, suggesting a direct relationship between stimulation of Cl- uptake and production of active chlorine compounds in the leucocyte.

Biological Transport↗
PubMed1998

Respiratory symptoms, bronchial responsiveness, and cellular characteristics of induced sputum in elite swimmers.

To investigate respiratory symptoms, increased bronchial responsiveness, and signs of airway inflammation in elite swimmers, we examined 29 swimmers from the Finnish national team and 19 healthy control subjects (nonasthmatic, symptom-free). They answered a questionnaire and were interviewed for respiratory symptoms. Lung volumes were measured and bronchial responsiveness assessed by a histamine challenge test. Induced sputum samples were also collected. Fourteen (48%) of the swimmers and three (16%) of the control subjects showed increased bronchial responsiveness (P<0.05). The sputum cell differential counts of eosinophils (mean 2.7% vs 0.2%) and neutrophils (54.7% vs 29.9%) from swimmers were significantly higher than those from controls (P<0.01). Eosinophilia (sputum differential eosinophil count of >4%) was observed in six (21%) of the swimmers and in none of the controls (P<0.05). Symptomatic swimmers had significantly more sputum eosinophils than did the symptom-free. The concentrations of sputum eosinophil peroxidase (EPO) and human neutrophil lipocalin (HNL) were significantly higher in swimmers than control subjects (P<0.001 and P=0.05). We conclude that elite swimmers had significantly more often increased bronchial responsiveness than control subjects. Sputum from swimmers contained a higher percentage of eosinophils and neutrophils, and higher concentrations of EPO and HNL than sputum from controls. Long-term and repeated exposure to chlorine compounds in swimming pools during training and competition may contribute to the increased occurrence of bronchial hyperresponsiveness and airway inflammation in swimmers.

Adolescent↗
PubMed2007

Identification of acetate-utilizing Bacteria and Archaea in methanogenic profundal sediments of Lake Kinneret (Israel) by stable isotope probing of rRNA.

Acetate is an important intermediate in the decomposition of organic matter in anoxic freshwater sediments. Here, we identified distinct microorganisms active in its oxidation and transformation to methane in the anoxic methanogenic layers of Lake Kinneret (Israel) profundal sediment by rRNA-based stable isotope probing (RNA-SIP). After 18 days of incubation with amended [U-(13)C]acetate we found that archaeal 16S rRNA was (13)C-labelled to a far greater extent than bacterial rRNA. We identified acetoclastic methanogens related to Methanosaeta concilii as being most active in the degradation and assimilation of acetate. Oxidation of the acetate-methyl group played only a minor role, but nevertheless 'heavy'(13)C-labelled bacterial rRNA templates were identified. 'Heavy' bacteria were mainly affiliated with the Betaproteobacteria (mostly Rhodocyclales and Nitrosomonadales), the Nitrospira phylum (related to 'Magnetobacterium bavaricum' and Thermodesulfovibrio yellowstonii), and also with the candidate phylum 'Endomicrobia'. However, the mode of energy gain that allowed for the assimilation of (13)C-acetate by these bacterial groups remains unknown. It may have involved syntrophic oxidation of acetate, reduction of chlorinated compounds, reduction of humic substances, fermentation of organic compounds, or even predation of (13)C-labelled Methanosaeta spp. In summary, this SIP experiment shows that acetate carbon was predominantly consumed by acetoclastic methanogens in profundal Lake Kinneret sediment, while it was also utilized by a small and heterogeneous community of bacteria.

Acetates↗
PubMed1992

Genetics and molecular biology of methanotrophs.

Over the last 20 years or so, the obligate methane-oxidizing bacteria (methanotrophs) have attracted considerable interest. As they grow on a relatively cheap and abundant carbon source, they appeared ideal organisms for the production of bulk chemicals, single-cell protein and for use in biotransformations. More recently their cooxidation properties have been investigated for bioremediation, including the removal of chlorinated compounds such as trichloroethylene from polluted groundwaters. These studies have resulted in a great deal of information on the physiology and biochemistry of methanotrophs but sadly the molecular biology and genetic studies of these organisms have lagged behind. This has been in part due to the obligate nature of the methanotrophs and the refractory nature of such organisms to conventional genetic analysis. However, the more recent availability of broad-host range plasmids coupled with improvements in molecular biology methods have allowed the development of molecular genetic techniques for methanotrophs. The purpose of this review is to summarize what is known about the genetics and molecular biology of methanotrophs and how this information can be used to complement previous and current biochemical studies on the unique property of these bacteria, i.e. the ability to oxidize methane to methanol. Recent developments in molecular ecology techniques that may be applied to these apparently ubiquitous organism are also considered.

Amino Acid Sequence↗
PubMed1994

Plasmid-mediated degradation of hydroxylated, methoxylated, and carboxylated benzene derivatives in Moraxella sp.

Chemical industries produce wastewater that contains large amount of aromatic substances including chlorinated compounds. Moraxella sp. isolated from a petroleum refinery unit efficiently used a variety of benzene derivatives bearing hydroxyl, methoxyl, carboxyl, and chloro- groups as the sole carbon source. The isolate harbored two plasmids of high mobility that are responsible for the utilization of these substrates.

Benzene Derivatives↗
PubMed1996

Melting of H2SO4&middot;4H2O Particles upon Cooling: Implications for Polar Stratospheric Clouds

Polar stratospheric clouds (PSCs) are important for the chemical activation of chlorine compounds and subsequent ozone depletion. Solid PSCs can form on sulfuric acid tetrahydrate (SAT) (H2SO4&middot;4H2O) nuclei, but recent laboratory experiments have shown that PSC nucleation on SAT is strongly hindered. A PSC formation mechanism is proposed in which SAT particles melt upon cooling in the presence of HNO3 to form liquid HNO3-H2SO4-H2O droplets 2 to 3 kelvin above the ice frost point. This mechanism offers a PSC formation temperature that is defined by the ambient conditions and sets a temperature limit below which PSCs should form.

Journal Article↗
PubMed1991

Dechlorination of chlorocatechols by stable enrichment cultures of anaerobic bacteria.

Metabolically stable anaerobic cultures obtained by enrichment with 5-bromovanillin, 5-chlorovanillin, catechin, and phloroglucinol were used to study dechlorination of chlorocatechols. A high degree of specificity in dechlorination was observed, and some chlorocatechols were appreciably more resistant to dechlorination than others: only 3,5-dichlorocatechol, 4,5-dichlorocatechol, 3,4,5-trichlorocatechol, and tetrachlorocatechol were dechlorinated, and not all of them were dechlorinated by the same consortium. 3,5-Dichlorocatechol produced 3-chlorocatechol, 4,5-dichlorocatechol produced 4-chlorocatechol, and 3,4,5-trichlorocatechol produced either 3,5-dichlorocatechol or 3,4-dichlorocatechol; tetrachlorocatechol produced only 3,4,6-trichlorocatechol. Incubation of uncontaminated sediments without additional carbon sources brought about dechlorination of 3,4,5-trichlorocatechol to 3,5-dichlorocatechol. O-demethylation of chloroguaiacols was generally accomplished by enrichment cultures, except that catechin enrichment was unable to O-demethylate tetrachloroguaiacol. None of the enrichments dechlorinated any of the polychlorinated phenols examined. The results suggested that dechlorination was not dependent on enrichment with or growth at the expense of chlorinated compounds and that it would be premature to formulate general rules for the structural dependence of the dechlorination reaction.

Journal Article↗
PubMed1998

Oxidation of trichloroethylene, 1,1-dichloroethylene, and chloroform by toluene/o-xylene monooxygenase from Pseudomonas stutzeri OX1.

Toluene/o-xylene monooxygenase (ToMO) from Pseudomonas stutzeri OX1, which oxidizes toluene and o-xylene, was examined for its ability to degrade the environmental pollutants trichloroethylene (TCE), 1, 1-dichloroethylene (1,1-DCE), cis-1,2-DCE, trans-1,2-DCE, chloroform, dichloromethane, phenol, 2,4-dichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, 2,3,5,6-tetrachlorophenol, and 2,3,4,5, 6-pentachlorophenol. Escherichia coli JM109 that expressed ToMO from genes on plasmid pBZ1260 under control of the lac promoter degraded TCE (3.3 microM), 1,1-DCE (1.25 microM), and chloroform (6.3 microM) at initial rates of 3.1, 3.6, and 1.6 nmol/(min x mg of protein), respectively. Stoichiometric amounts of chloride release were seen, indicating mineralization (2.6, 1.5, and 2.3 Cl- atoms per molecule of TCE, 1,1-DCE, and chloroform, respectively). Thus, the substrate range of ToMO is extended to include aliphatic chlorinated compounds.

Biodegradation, Environmental↗
PubMed2003

Characterization of two tetrachloroethene-reducing, acetate-oxidizing anaerobic bacteria and their description as Desulfuromonas michiganensis sp. nov.

Two tetrachlorethene (PCE)-dechlorinating populations, designated strains BB1 and BRS1, were isolated from pristine river sediment and chloroethene-contaminated aquifer material, respectively. PCE-to-cis-1,2-dichloroethene-dechlorinating activity could be transferred in defined basal salts medium with acetate as the electron donor and PCE as the electron acceptor. Taxonomic analysis based on 16S rRNA gene sequencing placed both isolates within the Desulfuromonas cluster in the delta subdivision of the Proteobacteria. PCE was dechlorinated at rates of at least 139 nmol min(-1) mg of protein(-1) at pH values between 7.0 and 7.5 and temperatures between 25 and 30 degrees C. Dechlorination also occurred at 10 degrees C. The electron donors that supported dechlorination included acetate, lactate, pyruvate, succinate, malate, and fumarate but not hydrogen, formate, ethanol, propionate, or sulfide. Growth occurred with malate or fumarate alone, whereas oxidation of the other electron donors depended strictly on the presence of fumarate, malate, ferric iron, sulfur, PCE, or TCE as an electron acceptor. Nitrate, sulfate, sulfite, thiosulfate, and other chlorinated compounds were not used as electron acceptors. Sulfite had a strong inhibitory effect on growth and dechlorination. Alternate electron acceptors (e.g., fumarate or ferric iron) did not inhibit PCE dechlorination and were consumed concomitantly. The putative fumarate, PCE, and ferric iron reductases were induced by their respective substrates and were not constitutively present. Sulfide was required for growth. Both strains tolerated high concentrations of PCE, and dechlorination occurred in the presence of free-phase PCE (dense non-aqueous-phase liquids). Repeated growth with acetate and fumarate as substrates yielded a BB1 variant that had lost the ability to dechlorinate PCE. Due to the 16S rRNA gene sequence differences with the closest relatives and the unique phenotypic characteristics, we propose that the new isolates are members of a new species, Desulfuromonas michiganensis, within the Desulfuromonas cluster of the Geobacteraceae.

Acetic Acid↗
PubMed1988

Isolation and characterization of a new plasmid from a Flavobacterium sp. which carries the genes for degradation of 2,4-dichlorophenoxyacetate.

A Flavobacterium sp. (strain 50001), capable of degrading 2,4-dichlorophenoxyacetate (2,4-D), 2-methyl-4-chlorophenoxyacetate, and 2-chlorobenzoate and imparting resistance to mercury, harbored a degradative plasmid, pRC10. Cured strains of the Flavobacterium sp. lost the plasmid as well as the ability to degrade these chlorinated compounds. Comparison of this plasmid with the well-characterized 2,4-D-degradative plasmid pJP4 from Alcaligenes eutrophus showed regions of homology between the two plasmids. Restriction fragments of plasmid pRC10 which shared homology with the regions conferring 2,4-D-degradative genes (tfd) of plasmid pJP4 were cloned into a broad-host-range plasmid and studied in Pseudomonas putida. From the results obtained, the cloned DNA fragment expressed the genes for 2,4-D monooxygenase (tfdA) and 2,4-dichlorophenol hydroxylase (tfdB). In spite of the similarity in function, the size (45 kilobases) and restriction pattern of plasmid pRC10 were considerably different from those of pJP4 (80 kilobases). This may be due to the difference in the microbial background during evolution of the two plasmids.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1998

The atrazine catabolism genes atzABC are widespread and highly conserved.

Pseudomonas strain ADP metabolizes the herbicide atrazine via three enzymatic steps, encoded by the genes atzABC, to yield cyanuric acid, a nitrogen source for many bacteria. Here, we show that five geographically distinct atrazine-degrading bacteria contain genes homologous to atzA, -B, and -C. The sequence identities of the atz genes from different atrazine-degrading bacteria were greater than 99% in all pairwise comparisons. This differs from bacterial genes involved in the catabolism of other chlorinated compounds, for which the average sequence identity in pairwise comparisons of the known members of a class ranged from 25 to 56%. Our results indicate that globally distributed atrazine-catabolic genes are highly conserved in diverse genera of bacteria.

Atrazine↗