Assessment of the toxicity of weathered petroleum hydrocarbon impacted soils to native plants from a site in the Canadian Subarctic.

Remedial guidelines for petroleum hydrocarbons (PHCs) in soil aid in the mitigation of risks to human health and the environmental. However, some remediation guidelines may overestimate the potential for adverse effects to native plant species, contributing to unnecessary remedial efforts in attempts to meet the guidelines. At sites where PHC-contaminated soils undergo weathering, some PHCs may persist but with decreased bioavailability to organisms. In this study, the toxicity of both coarse and fine-grained subarctic soils, contaminated with weathered PHCs were assessed using five native plant species (Picea mariana, Achillea millefolium, Alnus viridis, Elymus trachycaulus and Salix bebbiana). Soil toxicity tests were conducted in a growth chamber with parameters set to simulate the site's subarctic climate conditions. Reference toxicant tests using boric acid were conducted to provide confidence in the interpretation of the results for the PHC-contaminated soils, and also provide new information on the sensitivities of the four boreal species to boric acid. All plants exhibited reduced growth and germination rates as boric acid concentrations increased. Despite exceeding the Canada-wide standard guidelines for Fraction 3 PHCs, field-collected contaminated soils had no significant negative impacts on the growth (i.e., length, dry weight and emergence) of any of the plant species tested.

Microbial community and potential functional gene diversity involved in anaerobic hydrocarbon degradation and methanogenesis in an oil sands tailings pond.

Oil sands tailings ponds harbor large amounts of tailings resulting from surface mining of bitumen and consist of water, sand, clays, residual bitumen, and hydrocarbon diluent. Oxygen ingress in these ponds is limited to the surface layers, causing most hydrocarbon degradation to be catalyzed by anaerobic, methanogenic microbial communities. This causes the evolution of large volumes of methane of up to 10(4) m(3)/day. A pyrosequencing survey of 16S rRNA amplicons from 10 samples obtained from different depths indicated the presence of a wide variety of taxa involved in anaerobic hydrocarbon degradation and methanogenesis, including the phyla Proteobacteria, Euryarchaeota, Firmicutes, Actinobacteria, Chloroflexi, and Bacteroidetes. Metagenomic sequencing of DNA isolated from one of these samples indicated a more diverse community than indicated by the 16S rRNA amplicon survey. Both methods indicated the same major phyla to be present. The metagenomic dataset indicated the presence of genes involved in the three stages of anaerobic aromatic hydrocarbon degradation, including genes for enzymes of the peripheral (upper), the central (lower), and the methanogenesis pathways. Upper pathway genes showed broad phylogenetic affiliation (Proteobacteria, Firmicutes, and Actinobacteria), whereas lower pathway genes were mostly affiliated with the Deltaproteobacteria. Genes for both hydrogenotrophic and acetotrophic methanogenesis were also found. The wide variety of taxa involved in initial hydrocarbon degradation through upper pathways may reflect the variety of residual bitumen and diluent components present in the tailings pond.

Assessment of insulin sensitivity (S I) and glucose effectiveness (S G) from a standardized hyperglucidic breakfast test in type 2 diabetics exhibiting various levels of insulin resistance.

We investigated the measurement of insulin sensitivity (S I) with a standardized hyperglucidic breakfast (SHB) compared to minimal model analysis of an intravenous glucose tolerance test (S I-IVGTT) in 17 patients clinically referred as type 2 diabetics, not yet treated by insulin, and representing a wide range of body mass index and S I. To classify the patients, ten meal-tolerance test-based calculations of S I (MTT-S I) were compared to S I-IVGTT, and their reference values and distribution were measured on a separate sample of 200 control SHBs and 209 control IVGTTs. Eight MTT-SI indices exhibit significant correlations with S I-IVGTT: Mari's OGIS index, BIGTT-SI|0-30-120, BIGTT-SI|0-60-120, 1/G b I m, Caumo's oral minimal model (OMM), Sluiter's index "A" = 10(4)/(I p·G p), Matsuda's composite index given by the formula ISIcomp = 10(4)/(I b G b I m G m)(0.5), S I = 1/I b G b I m G m with r (2) ranging between 0,53 and 0,28. S I-IVGTT and S I-MTT exhibited in the lower range a very different (non-normal) pattern of distribution and thus the cutoff value for defining insulin resistance varied among indices. With such cutoffs, S I-MTT < 6.3 min(-1)/(µU/ml) 10(-4) with Caumo's OMM was the best predictor of insulin resistance defined as S I-IVGTT < 2 min(-1)/(µU/ml) 10(-4). Other indices, including OGIS and BIGTT, resulted in more misclassifications of patients. HOMA-IR and QUICKI were poor predictors. The formula [Formula: see text] satisfactorily predicts IVGTT-derived glucose effectiveness in type 2 diabetics. Thus, SHB appears suitable for the measurement of S I and S G in type 2 diabetics, and the OMM seems to provide the most accurate SHB-derived index in this population.

Carbon and sulfur cycling by microbial communities in a gypsum-treated oil sands tailings pond.

Oil sands tailings ponds receive and store the solid and liquid waste from bitumen extraction and are managed to promote solids densification and water recycling. The ponds are highly stratified due to increasing solids content as a function of depth but can be impacted by tailings addition and removal and by convection due to microbial gas production. We characterized the microbial communities in relation to microbial activities as a function of depth in an active tailings pond routinely treated with gypsum (CaSO(4)·2H(2)O) to accelerate densification. Pyrosequencing of 16S rDNA gene sequences indicated that the aerobic surface layer, where the highest level of sulfate (6 mM) but no sulfide was detected, had a very different community profile than the rest of the pond. Deeper anaerobic layers were dominated by syntrophs (Pelotomaculum, Syntrophus, and Smithella spp.), sulfate- and sulfur-reducing bacteria (SRB, Desulfocapsa and Desulfurivibrio spp.), acetate- and H(2)-using methanogens, and a variety of other anaerobes that have been implicated in hydrocarbon utilization or iron and sulfur cycling. The SRB were most abundant from 10 to 14 mbs, bracketing the zone where the sulfate reduction rate was highest. Similarly, the most abundant methanogens and syntrophs identified as a function of depth closely mirrored the fluctuating methanogenesis rates. Methanogenesis was inhibited in laboratory incubations by nearly 50% when sulfate was supplied at pond-level concentrations suggesting that in situ sulfate reduction can substantially minimize methane emissions. Based on our data, we hypothesize that the emission of sulfide due to SRB activity in the gypsum treated pond is also limited due to its high solubility and oxidation in surface waters.

Relation between the activity of anaerobic microbial populations in oil sands tailings ponds and the sedimentation of tailings.

Oil sands tailings ponds contain a variety of anaerobic microbes, including methanogens, sulfate- and nitrate-reducing bacteria. Methanogenic activity in samples from a tailings pond and its input streams was higher with trimethylamine (TMA) than with acetate. Methanogens closely affiliated to Methanomethylovorans hollandica were found in the TMA enrichments. Tailings sedimentation increased with methanogenic activity, irrespective whether TMA or acetate was used to stimulate methanogenesis. Increased sedimentation of autoclaved tailings was observed with added pure cultures under methanogenic, as well as under nitrate-reducing conditions, but not under sulfate-reducing conditions. Scanning electron microscopy and energy-dispersive X-ray spectroscopy indicated the presence of microbes and of extracellular polymeric substances in tailings particle aggregates, especially under methanogenic and nitrate-reducing conditions. Hence different classes of microorganisms growing in tailings ponds contribute to increased tailings aggregation and sedimentation. Because addition of nitrate is known to lower methane production by methanogenic consortia, these observations offer the potential to combine lower methane emissions with improved microbially-induced tailings sedimentation.

Diversity of ring-hydroxylating dioxygenases in pristine and oil contaminated microbial mats at genomic and transcriptomic levels.

The aim of this work was to characterize bacterial ring-hydroxylating dioxygenase (RHD) diversity in a pristine microbial mat and follow their diversity changes in response to heavy fuel oil contamination. In order to describe the RHDs diversity, new degenerate primers were designed and a nested-PCR approach was developed to gain sensitivity and wider diversity. RHD diversity in artificially contaminated mats maintained in microcosms and in chronically contaminated mats was analysed by clone libraries and terminal restriction fragment length polymorphism (T-RFLP) at genomic and transcriptomic levels. The RHD diversity in the pristine microbial mat was represented by Pseudomonas putida nahAc-like genes and no increase of diversity was detected after 1 year of oil contamination. The diversity observed in a 30 year chronically polluted microbial mat was represented by four main RHD clusters and two new genes revealing higher polyaromatic hydrocarbon (PAH) degradation capacity. This study illustrates that a single petroleum contamination (such as oil spill) is not enough to involve a detectable modification of RHD diversity. The new degenerate primers described here allowed RHD gene amplification from pristine and contaminated samples thereby showing their diversity. The proposed approach solves one of the main problems of functional gene analysis providing effective amplification of the environmental diversity of the targeted genes.

[Physical exercise and insulin resistance: from muscle metabolic physiopathology to therapeutics]. / Exercice physique et insulinorésistance: de la physiopathologie métabolique musculaire à l'intervention thérapeutique.

Insulin resistance which characterises obesity and type 2 diabetes depends on genetic and environmental factors. Sedentarity plays a key role in the development of insulin resistance and skeletal muscle of obese or type 2 diabetes patients shows several abnormalities of carbohydrate and fat metabolism. Exercice training by its beneficial effects on skeletal muscle and particularly on mitochondrial function is efficient to prevent and to treat obesity and type 2 diabetes.

Effects of heavy fuel oil on the bacterial community structure of a pristine microbial mat.

The effects of petroleum contamination on the bacterial community of a pristine microbial mat from Salins-de-Giraud (Camargue, France) have been investigated. Mats were maintained as microcosms and contaminated with no. 2 fuel oil from the wreck of the Erika. The evolution of the complex bacterial community was monitored by combining analyses based on 16S rRNA genes and their transcripts. 16S rRNA gene-based terminal restriction fragment length polymorphism (T-RFLP) analyses clearly showed the effects of the heavy fuel oil after 60 days of incubation. At the end of the experiment, the initial community structure was recovered, illustrating the resilience of this microbial ecosystem. In addition, the responses of the metabolically active bacterial community were evaluated by T-RFLP and clone library analyses based on 16S rRNA. Immediately after the heavy fuel oil was added to the microcosms, the structure of the active bacterial community was modified, indicating a rapid microbial mat response. Members of the Gammaproteobacteria were initially dominant in the contaminated microcosms. Pseudomonas and Acinetobacter were the main genera representative of this class. After 90 days of incubation, the Gammaproteobacteria were superseded by "Bacilli" and Alphaproteobacteria. This study shows the major changes that occur in the microbial mat community at different time periods following contamination. At the conclusion of the experiment, the RNA approach also demonstrated the resilience of the microbial mat community in resisting environmental stress resulting from oil pollution.

Simvastatin induces impairment in skeletal muscle while heart is protected.

3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) are widely used to reduce plasma cholesterol concentration. However, statins are also known to induce various forms of muscular toxicity. We have previously shown that acute application of simvastatin on human skeletal muscle samples induced a cascade of cellular events originating from mitochondria and resulting in a global alteration of Ca2+ homeostasis. The present study was designed to further define the origin of the mitochondria impairment and to understand the apparent lack of deleterious effect on the heart. Using fluorescence imaging analysis and oxygraphy on human and rat skinned skeletal muscle samples, we show that the simvastatin-induced mitochondria impairment results from inhibition of the complex I of respiratory chain. Similar simvastatin-induced mitochondria impairment and alteration of Ca2+ homeostasis occur in permeabilized but not in intact ventricular rat cardiomyocytes. In intact rat skeletal muscle fibers from the flexor digitorum brevis muscle, the simvastatin-induced alteration of Ca2+ homeostasis is abolished when monocarboxylate transporter (MCT4) is inhibited. The impairment of complex I by simvastatin might be the primary step of its cellular deleterious effects leading to muscle fiber death. This mechanism is seen specifically in skeletal muscles. This specificity should be in part attributed to a preferential uptake of statins by MCT4 that is not expressed in cardiomyocytes.

Mutations at residues 282, 286, and 293 of phage lambda integrase exert pathway-specific effects on synapsis and catalysis in recombination.

Bacteriophage lambda integrase (Int) catalyzes site-specific recombination between pairs of attachment (att) sites. The att sites contain weak Int-binding sites called core-type sites that are separated by a 7-bp overlap region, where cleavage and strand exchange occur. We have characterized a number of mutant Int proteins with substitutions at positions S282 (S282A, S282F, and S282T), S286 (S286A, S286L, and S286T), and R293 (R293E, R293K, and R293Q). We investigated the core- and arm-binding properties and cooperativity of the mutant proteins, their ability to catalyze cleavage, and their ability to form and resolve Holliday junctions. Our kinetic analyses have identified synapsis as the rate-limiting step in excisive recombination. The IntS282 and IntS286 mutants show defects in synapsis in the bent-L and excisive pathways, respectively, while the IntR293 mutants exhibit synapsis defects in both the excision and bent-L pathways. The results of our study support earlier findings that the catalytic domain also serves a role in binding to core-type sites, that the core contacts made by this domain are important for both synapsis and catalysis, and that Int contacts core-type sites differently among the four recombination pathways. We speculate that these residues are important for the proper positioning of the catalytic residues involved in the recombination reaction and that their positions differ in the distinct nucleoprotein architectures formed during each pathway. Finally, we found that not all catalytic events in excision follow synapsis: the attL site probably undergoes several rounds of cleavage and ligation before it synapses and exchanges DNA with attR.