Michel Joyeux

Variations of bacterial 16S rDNA phylotypes prior to and after chlorination for drinking water production from two surface water treatment plants

We examined the variations of bacterial populations in treated drinking water prior to and after the final chlorine disinfection step at two different surface water treatment plants. For this purpose, the bacterial communities present in treated water were sampled after granular activated carbon (GAC) filtration and chlorine disinfection from two drinking water treatment plants supplying the city of Paris (France). Samples were analyzed after genomic DNA extraction, polymerase chain reaction (PCR) amplification, cloning, and sequencing of a number of 16S ribosomal RNA (rRNA) genes. The 16S rDNA sequences were clustered into operational taxonomic units (OTUs) and the OTU abundance patterns were obtained for each sample. The observed differences suggest that the chlorine disinfection step markedly affects the bacterial community structure and composition present in GAC water. Members of the Alphaproteobacteria and Betaproteobacteria were found to be predominant in the GAC water samples after phylogenetic analyses of the OTUs. Following the chlorine disinfection step, numerous changes were observed, including decreased representation of Proteobacteria phylotypes. Our results indicate that the use of molecular methods to investigate changes in the abundance of certain bacterial groups following chlorine-based disinfection will aid in further understanding the bacterial ecology of drinking water treatment plants (DWTPs), particularly the disinfection step, as it constitutes the final barrier before drinking water distribution to the consumer’s tap.

Bioavailability and intestinal absorption of aluminum in rats: effects of aluminum compounds and some dietary constituents.

In the present investigation, the deposition of aluminum in intestinal fragment and the appearance in blood were studied in a perfused rat intestine in situ for 1 h with several aluminum forms (16 mM). We observed that aluminum absorption was positively correlated with the theoretic affinity of aluminum and the functional groups of the chelating agent. The absorption of aluminum after ingestion of organic compounds is more important than after ingestion of mineral compounds, with the following order: Al citrate > Al tartrate, Al gluconate, Al lactate > Al glutamate, Al chloride, Al sulfate, Al nitrate. Absorption depends on the nature of the ligands associated with the Al3+ ion in the gastrointestinal fluid. The higher the aluminum retention in intestinal fragment, the lower the absorption and appearance in blood. However, the higher aluminum concentration is always in the jejunal fragment because of the influence of pH variation on this fragment. Another objective of the present study was to determine the influence of several parameters on aluminum citrate absorption: with or without 0.1 mmol dinitrophenol/L, with aluminum concentration from 3.2, 16, 32, and 48, to 64 mmol/L, media containing 0, 3, or 6 mmol Ca/L, with or without phosphorus or glucose. It is concluded that aluminum is absorbed from the gastrointestinal tract by (1) a paracellular energy independent and nonsaturable route, mainly used for high aluminum concentration, which is modified by extracellular calcium, and (2) a transcellular and saturable route, the aluminum level was not modified with enhancement of aluminum quantity in intestinal lumen. This pathway can be similar with calcium transfer through the intestine and is energy dependent because of a decrease of aluminum absorption that follows the removal of glucose and phosphorus.

Variations in trihalomethane levels in three French water distribution systems and the development of a predictive model.

Epidemiological studies have demonstrated that chlorination by-products in drinking water may cause some types of cancer in humans. However, due to differences in methodology between the various studies, it is not possible to establish a dose-response relationship. This shortcoming is due primarily to uncertainties about how exposure is measured-made difficult by the great number of compounds present-the exposure routes involved and the variation in concentrations in water distribution systems. This is especially true for trihalomethanes for which concentrations can double between the water treatment plant and the consumer tap. The aim of this study is to describe the behaviour of trihalomethanes in three French water distribution systems and develop a mathematical model to predict concentrations in the water distribution system using data collected from treated water at the plant (i.e. the entrance of the distribution system). In 2006 and 2007, samples were taken successively from treated water at the plant and at several points in the water distribution system in three French cities. In addition to the concentrations of the four trihalomethanes (chloroform, dichlorobromomethane, chlorodibromomethane, bromoform), many other parameters involved in their formation that affect their concentration were also measured. The average trihalomethane concentration in the three water distribution systems ranged from 21.6 μg/L to 59.9 μg/L. The increase in trihalomethanes between the treated water at the plant and a given point in the water distribution system varied by a factor of 1.1-5.7 over all of the samples. A log-log linear regression model was constructed to predict THM concentrations in the water distribution system. The five variables used were trihalomethane concentration and free residual chlorine for treated water at the plant, two variables that characterize the reactivity of organic matter (specific UV absorbance (SUVA), an indicator developed for the free chlorine consumption in the treatment plant before distribution δ) and water residence time in the distribution system. French regulations impose a minimum trihalomethane level for drinking water and most tests are performed on treated water at the plant. Applied in this context, the model developed here helps better to understand trihalomethane exposure in the French population, particularly useful for epidemiological studies.

Effects of Subchronic Exposure to Manganese Chloride on Tissue Distribution of Three Essential Elements in Rats

A subchronic treatment of manganese chloride (MnCl2) was administered to rats by intraperitoneal (IP) route (6 mg Mn/kg of body weight/day) or oral (PO) route (75 mg Mn/kg of body weight/day) for 4 weeks. After a 2-week interval, different tissues plus the blood were sampled. An increase of manganese (Mn) concentrations was observed in most of the tissues, particularly in the nervous system (brain and spinal cord) and in femur, with the exception of liver, adrenal glands, and esophagus by IP treatment and liver, jejunum, ileum, and adipose tissue by PO treatment. Tissue accumulation of Mn was greater by IP treatment. During each of the two treatments, urinary and fecal excretion of Mn increased. The presence of Mn observed in whole blood, bone marrow, and spleen after IP treatment could be explained by the existence of competition between iron (Fe) and Mn that may appear, notably, as a disturbance in the functioning of the respiratory chain in the cells (incomplete O2 reduction and formation of free radicals and oxygenated compounds), leading to cellular degeneration. In these experimental conditions, no obvious competition could be observed with zinc (Zn) and copper (Cu). Despite a large accumulation of Mn in the bones, no disturbance of the phosphorus-calcium metabolism was observed.

Nickel Absorption and Distribution from Rat Small Intestine In Situ

The aim of this work was to study the absorption of nickel chloride in rats by means of the intestinal perfusion in situ technique at nickel concentrations of 1, 5, 10, 25, and 100 mg/L. Active transport and facilitated diffusion seem to play an important role in the intestinal absorption of nickel at concentrations≤10 mg/L. At higher concentrations, the absorption rate would be limited by saturation of the carriers. The distribution of the absorbed nickel was studied by intestinal perfusion of a 10-mg Ni/L solution for 30 or 60 min. Both in concentration and amount, the jejunum showed the higher values of absorbed nickel, followed by the kidneys and liver. When all of the collected organs (brain, heart, liver, lungs, spleen, kidneys, and testicles) and blood, but not the small intestine, are analyzed following a 60-min perfusion, it was found that 1% of the initial concentration had passed through the intestinal barrier.

Perchlorate: water and infant formulae contamination in France and risk assessment in infants

Perchlorate ions ClO4–, known to inhibit competitively the uptake of iodine by the thyroid, have been detected in drinking water in France as well as in infant formulae. A tolerable daily intake (TDI) has been established at 0.7 µg kg–1 bw day–1 based on the inhibition of iodine uptake. Due to this mechanism of action, the iodine status could strongly influence the biological effect of perchlorate. Perchlorate concentrations in water and infant formulae were measured and the exposure of children under 6 months of age calculated. It appeared that the TDI could be exceeded in some children. As the iodine status is not optimal within the entire French population, there appears to be a need to clarify the sources of perchlorate ultimately to decrease exposure.

Mycobacterium lutetiense sp. nov., Mycobacterium montmartrense sp. nov. and Mycobacterium arcueilense sp. nov., members of a novel group of non-pigmented rapidly growing mycobacteria recovered from a water distribution system.

From our recent survey of non-pigmented rapidly growing mycobacteria in the Parisian water system, three groups of isolates (taxons 1-3) corresponding to possible novel species were selected for taxonomic study. The three taxa each formed creamy white, rough colonies, had an optimal growth temperature of 30 °C, hydrolyzed Tween 80, were catalase-positive at 22 °C and expressed arylsulfatase activity. All three were susceptible to amikacin, ciprofloxacin and tigecycline. The three taxa produced specific sets of mycolic acids, including one family that has never previously been described, as determined by thin layer chromatography and nuclear magnetic resonance. The partial rpoB sequences (723 bp) showed 4-6 % divergence from each other and more than 5 % differences from the most similar species. Partial 16S rRNA gene sequences showed 99 % identity within each species. The most similar sequences for 16S rRNA genes (98-99 % identity over 1444-1461 bp) were found in the Mycobacterium fortuitum group, Mycobacterium septicum and Mycobacterium farcinogenes. The three taxa formed a new clade (bootstrap value, 99 %) on trees reconstructed from concatenated partial 16S rRNA, hsp65 and rpoB sequences. The above results led us to propose three novel species for the three groups of isolates, namely Mycobacterium lutetiense sp. nov. [type strain 071T=ParisRGMnew_1T (CIP 110656T=DSM 46713T)], Mycobacterium montmartrense sp. nov. [type strain 196T=ParisRGMnew_2T (CIP 110655T=DSM 46714T)] and Mycobacteriu marcueilense sp. nov. [type strain of 269T=ParisRGMnew_3T (CIP 110654T=DSM 46715T)].