Évolution de la qualité de l'eau dans le réseau de distribution de la ville de Montréal

Dans la présente étude, nous montrons l'évolution de l'eau dans un réseau de distribution. Ce réseau a été construit dans les années 70 à l'aide de conduites d'acier ou de fonte ductile munies d'un revêtement intérieur de ciment. Il est alimenté par des eaux de très bonne qualité qui circulent d'abord dans une suite de conduites maîtresses (de 2 700 mm à 900 mm) jusqu'à un secteur de petites conduites maillées (200 et 300 mm). Des échantillons d'eau ont été prélevés à 14 reprises durant une année, le long de la conduite maîtresse (le temps de séjour y varie de 0 h à 13,6 h) et dans le secteur de petites conduites (de 13,6 h à 18,4 h). Nous avons mesuré la température, le pH, plusieurs sous-produits de désinfection dont les trihalométhanes et les aldéhydes, le carbone organique total et biodégradable ainsi que les concentrations de bactéries hétérotrophes aérobies et anaérobies facultatives (BHA) et les comptes directs totaux mesurés en épifluorescence. Le réseau a très peu d'effet sur l'évolution des sous-produits de désinfection. En effet, les résultats obtenus à partir des échantillons témoins (eaux traitées conservées dans un flacon propre à la même température que dans le réseau) sont semblables à ceux obtenus à partir des eaux prélevées dans le réseau de distribution.Les concentrations de bactéries ainsi que les concentrations de CODB sont assez stables dans le réseau. Il est intéressant de noter qu'il y a de 0,2 à 0,45 mg/l de CODB, ce qui est supérieur à la concentration minimale de 0,15 mg/l requise pour la croissance des bactéries. Par contre, le chlore résiduel libre est toujours supérieur à 0,20 mg/l. Une seule exception, le 11 juillet 1994, dans le secteur de petites conduites, le chlore résiduel a baissé jusqu'à 0,16 mg/l. Durant cette journée, nous avons observé une légère augmentation des comptes directs totaux mesurés en épifluorescence.Studies were performed to follow the changes in water quality along a distribution system. The distribution system under study is divided into two parts: main pipes starting from the plant (from 2 700 mm to 900 mm diameter) feeding a small pipes sector (200 mm and 300 mm diameter). Residence times range from 0 to 13.6 hours in main pipes and from 13.6 h to 18.4 h in small pipes. All pipes are made of steel or ductile iron and their interior is lined with concrete; there is therefore little corrosion. Since the raw water is of such high quality, the treatment plant is very simple: a direct filtration on sand followed by ozonation and chlorine disinfection. Samples were taken on 14 occasions, during a full year period, in the distribution system and in the treatment plant after chlorination. These last samples were incubated in clean flasks at the network temperature. Measurements of temperature, pH, disinfection by-products (trihalomethanes, aldehydes, haloacetonitriles, haloacetones and chloropicrine), total organic carbon (TOC), biodegradable dissolved organic carbon (BDOC) and number of bacteria (heterotrophic plate count and total direct count by epifluorescence) were completed.The distribution network seems to have very little effect on chlorine demand and disinfection by-products. Results from water incubated in flasks are similar to those from distribution network. After more than 18 hours contact time, the chlorine residual is still higher than 0.2 mg/l in most of the samples taken in the distribution network and in the flask. It should be noted that the initial chlorine concentrations range from 0.65 mg/l (cold water) to 1.00 mg/l (warm water). Chlorine demand and trihalomethane (THM) curves are typical, a rapid increase with time followed by a relatively stable level. THM concentrations in the distribution network are low: a typical value of 14 µg/l after 13.6 hours contact time is detected. The maximum concentration of 43 µg/l of total THM was measured in a dead end. In this latter sample, 42 % of the THM was present as bromodichloromethane and 39 % as chloroform. Other by-products such as haloacetonitrile, haloacetone and chloropicrine were always detected in very small concentrations.Aldehyde concentrations in treated water were low, between 21 and 42 µg/l. These concentrations were stable throughout the distribution system. Fixed and free biomass seems to have very little effect on these biodegradable compounds. These results were confirmed by BDOC results. BDOC in treated water ranges from 0.2 to 0.45 mg/l and remains stable in the distribution system. These low BDOC concentrations and the chlorine residual of approximately 0.2 mg/l seem to be sufficient to prevent regrowth in the distribution system. Total direct counts by epifluorescence showed almost no increase of bacterial density except for the July 11th sample. This is the only day where the free chlorine residual dropped below 0.2 mg/l, with values of free chlorine residual dropping as low as 0.16 mg/l

Neurobiologie de la toxicomanie : avancées récentes et nouvelles stratégies d’intervention

Pendant longtemps, la toxicomanie a été associée sur le plan neurobiologique à la modulation à court terme de différents systèmes de neurotransmission. Les stratégies de traitement ciblaient conséquemment les récepteurs auxquels se lie directement la substance étant source d’abus. Ces approches ont contribué à améliorer le soulagement des symptômes d’intoxication et de sevrage, tout en favorisant l’accès à des services psychosociaux adaptés. Toutefois, les données soulignent, chez certains sous-groupes d’individus, l’efficacité parfois mitigée de ces interventions visant à diminuer de façon soutenue la consommation et les symptômes associés à la toxicomanie, particulièrement le craving. Les avancées récentes en neurosciences ont permis de mieux comprendre les mécanismes neurobiologiques expliquant la vulnérabilité à la rechute. D’une conception essentiellement dopaminergique et striatale, les théories biologiques de la toxicomanie intègrent maintenant la contribution des systèmes glutamatergique, opioïde et endocannabinoïde, de même que l’interaction entre ces différentes composantes au sein des structures corticales et sous-corticales. L’intérêt semble avoir migré des phénomènes neurobiologiques à court terme vers la modulation prolongée du fonctionnement des structures en jeu dans la toxicomanie. Ce changement de paradigmes a mené à l’émergence de plusieurs stratégies thérapeutiques visant à diminuer les risques de rechute en modulant de façon plus spécifique les circuits neuronaux dont le fonctionnement est altéré par la prise chronique de substances. Les systèmes endocannabinoïde et glutamatergique, notamment, apparaissent comme une cible de choix pour le traitement du craving et la prévention de la rechute. Le présent article a pour objectif de résumer certains des plus récents courants en matière de conceptualisation neurobiologique de la toxicomanie de même que les nouvelles pistes de traitement en découlant.For years, the neurobiology of drug addiction was characterized by the short-term modulation of different neurotransmission systems, therapeutic strategies directly targeting the receptors that are bound by substances. These approaches have helped to improve the treatment of drug intoxication and withdrawal, while promoting access to a broad array of psychosocial services. However, the data highlight the mixed effectiveness of these interventions to induce a sustained decrease in consumption and other symptoms of addiction, especially craving, among subgroups of individuals. Recent advances in neuroscience have led to a growing understanding of the neurobiological mechanisms underlying the vulnerability to relapse and other behaviors associated with addiction. The primarily dopaminergic and striatal hypothesis of these phenomena has been replaced by a theory incorporating the contribution of the glutamatergic, endocannabinoid and opioid systems, as well as the interaction between these various components within cortical and sub-cortical structures. The focus has moved from the short-term neurobiological changes to the long-lasting modulation of the structures involved in addiction. This paradigm shift led to the emergence of several therapeutic strategies that aim at reducing the risk of relapse by modulating specific neural circuits whose functions are altered by chronic substance use. The endocannabinoid and glutamate systems, in particular, are promising targets for the treatment of craving and relapse. This article aims to summarize some of the latest trends in the neurobiology of addiction as well as new avenues of treatment.Durante mucho tiempo la toxicomanía estuvo asociada en el plano neurobiológico con la modulación a corto plazo de diferentes sistemas de neurotransmisión. Las estrategias de tratamiento apuntaban, por consiguiente, a los receptores que se vinculan directamente con la sustancia que es el origen del abuso. Estos enfoques contribuyeron a mejorar el alivio de los síntomas de intoxicación y abstinencia, favoreciendo al mismo tiempo el acceso a servicios psicosociales adaptados. Sin embargo, en ciertos grupos de individuos, los datos destacan la eficacia a veces mitigada de estas intervenciones destinadas a disminuir de manera continua el consumo y los síntomas relacionados con la toxicomanía, particularmente el craving. Los recientes progresos de la neurociencia permitieron comprender mejor los mecanismos neurobiológicos que explican la vulnerabilidad ante la recaída. De concepción esencialmente dopaminérgica y estratial, las teorías biológicas de la toxicomanía integran ahora la contribución de los sistemas glutamatérgico, opiáceo y endocanabinoide, así como la interacción entre estos diferentes componentes dentro de las estructuras corticales y subcorticales. El interés parece haberse desplazado de los fenómenos neurobiológicos de corto plazo hacia la modulación prolongada del funcionamiento de las estructuras que están en juego en la toxicomanía. Este cambio de paradigmas condujo al surgimiento de numerosas estratégicas terapéuticas destinadas a disminuir los riesgos de recaída al modular más específicamente los circuitos neuronales cuyo funcionamiento está alterado por el consumo crónico de drogas. Los sistemas endocanabinoide y glutamatérgico, principalmente, aparecen como un objetivo a privilegiar para el tratamiento del craving y la prevención de la recaída. El presente artículo está destinado a resumir algunas de las más recientes corrientes en materia de conceptualización neurobiológica de la toxicomanía y las nuevas vías de tratamiento a las que dichas corrientes dan origen

Changes in Bacterial Growth Rate Govern Expression of the \u3cem\u3eBorrelia burgdorferi\u3c/em\u3e OspC and Erp Infection-Associated Surface Proteins

The Lyme disease spirochete controls production of its OspC and Erp outer surface proteins, repressing protein synthesis during colonization of vector ticks but increasing expression when those ticks feed on vertebrate hosts. Early studies found that the synthesis of OspC and Erps can be stimulated in culture by shifting the temperature from 23°C to 34°C, leading to a hypothesis that Borrelia burgdorferi senses environmental temperature to determine its location in the tick-mammal infectious cycle. However, borreliae cultured at 34°C divide several times faster than do those cultured at 23°C. We developed methods that disassociate bacterial growth rate and temperature, allowing a separate evaluation of each factor\u27s impacts on B. burgdorferi gene and protein expression. Altogether, the data support a new paradigm that B. burgdorferi actually responds to changes in its own replication rate, not temperature per se, as the impetus to increase the expression of the OspC and Erp infection-associated proteins

A Large Screen Identifies Beta-Lactam Antibiotics Which Can Be Repurposed To Target the Syphilis Agent

Syphilis, caused by the spirochete Treponema pallidum subsp. pallidum (hereafter called T. pallidum), is re-emerging as a worldwide sexually transmitted infection. A single intramuscular dose of benzathine penicillin G is the preferred syphilis treatment option. Both supply shortage concerns and the potential for acquired antibiotic resistance further the need to broaden the repertoire of syphilis therapeutics. We reasoned that other β-lactams may be equally or more effective at targeting the disease-causing agent, Treponema pallidum, but have yet to be discovered due to a previous lack of a continuous in vitro culture system. Recent technical advances with respect to in vitro T. pallidum propagation allowed us to conduct a high-throughput screen of almost 100 β-lactams. Using several molecular and cellular approaches that we developed or adapted, we identified and confirmed the efficacy of several β-lactams that were similar to or outperformed the current standard, benzathine penicillin G. These options are either currently used to treat bacterial infections or are synthetic derivatives of naturally occurring compounds. Our studies not only identified additional potential therapeutics in the resolution of syphilis, but provide techniques to study the complex biology of T. pallidum—a spirochete that has plagued human health for centuries

Eubacterial SpoVG homologs constitute a new family of site-specific DNA-binding proteins

A site-specific DNA-binding protein was purified from Borrelia burgdorferi cytoplasmic extracts, and determined to be a member of the highly conserved SpoVG family. This is the first time a function has been attributed to any of these ubiquitous bacterial proteins. Further investigations into SpoVG orthologues indicated that the Staphylococcus aureus protein also binds DNA, but interacts preferentially with a distinct nucleic acid sequence. Site-directed mutagenesis and domain swapping between the S. aureus and B. burgdorferi proteins identified that a 6-residue stretch of the SpoVG α-helix contributes to DNA sequence specificity. Two additional, highly conserved amino acid residues on an adjacent β-sheet are essential for DNA-binding, apparently by contacts with the DNA phosphate backbone. Results of these studies thus identified a novel family of bacterial DNA-binding proteins, developed a model of SpoVG-DNA interactions, and provide direction for future functional studies on these wide-spread proteins

\u3cem\u3eBorrelia burgdorferi\u3c/em\u3e cp32 BpaB Modulates Expression of the Prophage NucP Nuclease and SsbP Single-Stranded DNA-Binding Protein

The Borrelia burgdorferi BpaB proteins of the spirochete\u27s ubiquitous cp32 prophages are DNA-binding proteins, required both for maintenance of the bacteriophage episomes and for transcriptional regulation of the cp32 erp operons. Through use of DNase I footprinting, we demonstrate that BpaB binds the erp operator initially at the sequence 5′-TTATA-3′. Electrophoretic mobility shift assays indicated that BpaB also binds with high affinity to sites located in the 5′ noncoding regions of two additional cp32 genes. Characterization of the proteins encoded by those genes indicated that they are a single-stranded DNA-binding protein and a nuclease, which we named SsbP and NucP, respectively. Chromatin immunoprecipitation indicated that BpaB binds erp, ssbP, and nucP in live B. burgdorferi. A mutant bacterium that overexpressed BpaB produced significantly higher levels of ssbP and nucP transcript than did the wild-type parent

P16-49. Broad types of cytokines secreted by Gag-specific T cells from HIV infected patients on HAART

International audiencen.

\u3cem\u3eBorrelia burgdorferi\u3c/em\u3e SpoVG DNA- and RNA-Binding Protein Modulates the Physiology of the Lyme Disease Spirochete

The SpoVG protein of Borrelia burgdorferi, the Lyme disease spirochete, binds to specific sites of DNA and RNA. The bacterium regulates transcription of spoVG during the natural tick-mammal infectious cycle and in response to some changes in culture conditions. Bacterial levels of spoVG mRNA and SpoVG protein did not necessarily correlate, suggesting that posttranscriptional mechanisms also control protein levels. Consistent with this, SpoVG binds to its own mRNA, adjacent to the ribosome-binding site. SpoVG also binds to two DNA sites in the glpFKD operon and to two RNA sites in glpFKD mRNA; that operon encodes genes necessary for glycerol catabolism and is important for colonization in ticks. In addition, spirochetes engineered to dysregulate spoVG exhibited physiological alterations

BpaB, a Novel Protein Encoded by the Lyme Disease Spirochete\u27s Cp32 Prophages, Binds to Erp Operator 2 DNA

Borrelia burgdorferi produces Erp outer surface proteins throughout mammalian infection, but represses their synthesis during colonization of vector ticks. A DNA region 5′ of the start of erp transcription, Operator 2, was previously shown to be essential for regulation of expression. We now report identification and characterization of a novel erp Operator 2-binding protein, which we named BpaB. erp operons are located on episomal cp32 prophages, and a single bacterium may contain as many as 10 different cp32s. Each cp32 family member encodes a unique BpaB protein, yet the three tested cp32-encoded BpaB alleles all bound to the same DNA sequence. A 20-bp region of erp Operator 2 was determined to be essential for BpaB binding, and initial protein binding to that site was required for binding of additional BpaB molecules. A 36-residue region near the BpaB carboxy terminus was found to be essential for high-affinity DNA-binding. BpaB competed for binding to erp Operator 2 with a second B. burgdorferi DNA-binding protein, EbfC. Thus, cellular levels of free BpaB and EbfC could potentially control erp transcription levels

BpaB, a novel protein encoded by the Lyme disease spirochete’s cp32 prophages, binds to erp Operator 2 DNA

Borrelia burgdorferi produces Erp outer surface proteins throughout mammalian infection, but represses their synthesis during colonization of vector ticks. A DNA region 5′ of the start of erp transcription, Operator 2, was previously shown to be essential for regulation of expression. We now report identification and characterization of a novel erp Operator 2-binding protein, which we named BpaB. erp operons are located on episomal cp32 prophages, and a single bacterium may contain as many as 10 different cp32s. Each cp32 family member encodes a unique BpaB protein, yet the three tested cp32-encoded BpaB alleles all bound to the same DNA sequence. A 20-bp region of erp Operator 2 was determined to be essential for BpaB binding, and initial protein binding to that site was required for binding of additional BpaB molecules. A 36-residue region near the BpaB carboxy terminus was found to be essential for high-affinity DNA-binding. BpaB competed for binding to erp Operator 2 with a second B. burgdorferi DNA-binding protein, EbfC. Thus, cellular levels of free BpaB and EbfC could potentially control erp transcription levels