Détermination du niveau de toxicité des sédiments de rivière par le test de bioluminescence bactérienne

A partir de références bibliographiques encore réduites, les auteurs ont mis au point un protocole expérimental d'évaluation de la toxicité des sédiments de rivière, après extraction au dichlorométhane et mesure de la toxicité par le lest de Bioluminescence Bactérienne.Ce protocole simple appliqué à quarante-trois prélèvements correspondant à des situations de pollution diversifiées, a permis d'établir et de proposer une typologie des sédiments en fonction de leur niveau de toxicité.Correspondant à une approche nouvelle (tests biologiques de toxicité sur sédiments), la méthodologie apparaît particulièrement intéressante pour la gestion patrimoniale des cours d'eau (réseaux de surveillance, mise en évidence de situations de pollutions), et devrait être intégrée dans les opérations de mesure de l'impact des pollutions toxiques sur les écosystèmes aquatiques.As toxic substances in river water are not easy to detect and to measure, sediments able to precipitate them have been userd, successfully, to quaintly metals and a limited number of organics. Actually, analytical determinations, very expansive, time consuming and never exhaustive, are not an adequate means for a general estimation of the presence of toxic organic substances.Another developing approach consists in determining effects not the substances themselves (contained in the sediments) but their toxic effects on biotests applied directly on all the sediments or on the extracts. This approach has been used by relatively few teams, principally in North-America and in The Netherlands, in limited areas, to evaluate the local impacts of industrial effluents on sea and-or river waters. On the contrary, the object of this work is to measure the interest of this kind of approach, at a large Water Basin, first to establish the toxic profiles of rivers with areas of pollution, and second to constitute a memorization, susceptible of being compared at regular intervals for an estimation of general depollution policies .Based on data taken from the literature, an organic extraction of sediments with dichloromethane as solvent (without pretreatment) and photobacterium phosphoreum luminescence inhibition test were chosen. Actually, according to the literature, dichloromethane is the must convenient solvant and toxic activities of extracts are well correlated with organic toxic contents in the few cases where, exceptionally, the two approaches have been carried out simultaneously. Similarly, the bacterial luminescence test, Microtox (commercial name), quick and inexpensive, is well correlated with results from other biotests when, occasionally, both were utilised. Moreover, Microtox was well tested in the Agence laboratory.Different conditions of extraction were carefully tested, before the adoption of the definite protocol : whole sediments (10-g) are mixed (slow agitation in rolling flasks) for 6 hours with dichloromethane (100-mL) and sodium sulphate (50 g). Dichloromethane is then eliminated and the remaining solid materials are washed twice with fresh dichloromethane (2 x 20 mi). Dichloromethane extract and washings are collected, dried over sodium sulphate and concentrated (below 40 °C) to 1 mL, further adjusted to 3 mL. A portion measured accurately of this concentrate is added to ethanol and concentrated to remove dichloromethane.Bacterial bioluminescence tests, in duplicate, are performed on ethanol extracts, diluted (1 %) in salified (sodium chloride 2 %) distilled water. Estimates of the EC 50 (concentration causing a 50 % reduction in bioluminescence) obtained using linear regression analysis are converted into Toxic Units and referred to the net organic weight, measured separately, at 550 °C. This expression of results is particularly relevant when sediments with different organic net weights are compared.The protocol has been applied to sediments collected at 43 sites in the principal rivers of Rhône Méditerranée Corse Basin and in special distant from significant domestic and industrial activities.The toxic amplitude observed (ratio of l/200 between lowest and highest toxic units obtained with the panel) and the good reproductibility of the whole process (10 % to 25 %) were consistent with a trial subdivision in 5 classes as follow :Class 1 : Out of pollution - Class 2 : Moderate toxicity - Class 3 : Important toxicity - Class 4 : Very important toxicity - Class 5 : Exceptional toxicity.The relevancy of this classification was estimated when sediments were classed according to their toxic content. The classification proves to be correct in must cases. Exceptionally toxic sediments were collected in sites affected by large industries and agglomerations as (CHASSE and SAINT-VALLIER) on River Rhone near Lyon and important chemical plants, or GIVORS, on the small River GIER, markedly affected by many various industries. On the contrary sediments of moderate toxicity corresponded to sites relatively far from sources of important pollutions, e.g., ARLES on the River RHONE near the sea and a number of sites on the River SAONE. Moreover, when repeated sampling was performed on the same sites, the results were consistent, belonging to the same class of toxicity.The general object of this work was not to determine a definite classification of sediment toxicities, but to assess the relevancy of this approach. In our opinion, it was proved that bioassays on sediment extracts, and specially the bacterial bioluminescence assay, are a valuable tool, before the material impossibility to determine the toxic substances content. Moreover this approach could be used at the Basin. More investigations are necessary to define more accurately the number and level of toxic classes and e.g. to establish correlations with perturbations of benthic communities living in the sediments. It is also a contribution to the general knowledge and action based on biotests performed on effluents and different compartments of rivers

La serie estratigráfica del Gallo-Vilo (prov. de Málaga, España)

El macizo del Gallo-Vilo presenta una serie estratigráfica que comprende términos desde el Lias basal al Oligo-Mioceno, con numerosas lagunas estratigráficas y transgresiones. Constituye una unidad estratigráfica de la Zona Subbética meridional; se indican las relaciones con las unidades vecinas

Perkinsus marinus extracellular protease modulates survival of Vibrio vulnificus in eastern oyster (Crassostrea virginica) hemocytes

The in vitro effects of the Perkinsus marinus serine protease on the intracellular survival of Vibrio vulnificus in oyster hemocytes were examined by using a time-course gentamicin internalization assay. Results showed that protease-treated hemocytes were initially slower to internalize V. vulnificus than untreated hemocytes. After 1 h, the elimination of V. vulnificus by treated hemocytes was significantly suppressed compared with hemocytes infected with invasive and noninvasive controls. Our data suggest that the serine protease produced by P. marinas suppresses the vibriocidal activity of oyster hemocytes to effectively eliminate V. vulnificus, potentially leading to conditions favoring higher numbers of vibrios in oyster tissues

Swine influenza surveillance in East and Southeast Asia: a systematic review

East and Southeast Asia are important pig- and poultry-producing areas, where the majority of production takes place on small-scale farms with low biosecurity levels. This systematic review synthesizes data on swine influenza virology, serology and epidemiology in East and Southeast Asia. A total of 77 research articles, literature reviews and conference papers were selected and analyzed from 510 references retrieved from PubMed and ISI Web of KnowledgeSM. The number of published articles increased in the last 3 years, which may be attributed to improvement in monitoring and/or a better promotion of surveillance data. Nevertheless, large inequalities in surveillance and research among countries are underlined. Virological results represent the largest part of published data, while the serological and epidemiological features of swine influenza in East and Southeast Asia remain poorly described. The literature shows that there have been several emergences of swine influenza in the region, and also considerable evidence of multiple introductions of North American and avian-like European strains. Furthermore, several avian-origin strains are isolated from pigs, including H5 and H9 subtypes. However, their low seroprevalence in swine also shows that pigs remain poorly infected by these subtypes. We conclude that sero-epidemioligical investigations have been neglected, and that they may help to improve virological surveillance. Inter- and intra-continental surveillance of gene flows will benefit the region. Greater investment is needed in swine influenza surveillance, to improve our knowledge of circulating strains as well as the epidemiology and disease burden in the region.published_or_final_versio

Characterizing the Epigenetic and Transcriptomic Responses to Perkinsus marinus Infection in the Eastern Oyster Crassostrea virginica

© Copyright © 2020 Johnson, Sirovy, Casas, La Peyre and Kelly. Eastern oysters in the northern Gulf of Mexico are routinely infected with the protistan parasite Perkinsus marinus, the cause of the disease commonly known as dermo. Recent experimental challenges among Atlantic coast populations have identified both resistant and susceptible genotypes using comparative transcriptomics. While controlled experimental challenges are essential first assessments, expanding this analysis to field reared individuals provides an opportunity to identify key genomic signatures of infection that appear both in the laboratory and in the field. In this study we combined reduced representation bisulfite sequencing with 3′ RNA sequencing (Tag-seq) to describe two molecular phenotypes associated with infection in oysters outplanted at a common garden field site. These combined approaches allowed us to examine changes in DNA methylation and gene expression for a large number of individuals (n = 40) that developed infections during the course of a common garden outplant experiment. Our epigenetic analysis of DNA methylation identified significant changes in gene body methylation associated with increasing infection intensity, across genes associated with immune responses. There was a smaller transcriptomic response to increasing infection intensities with 32 genes showing differential expression; however, only 40% of these genes were found to also be differentially methylated. While there was no clear pattern between direction of differential methylation and gene expression, there was a significant effect of percent methylation on gene-by-gene expression levels and the coefficient of variation in gene body methylation between treatments. These results show that in C. virginica, heavily methylated genes have high levels of gene expression with low levels of variation. Comparing our differential expression results with previously published experimental P. marinus challenges identified overlapping expression patterns for genes associated with C1q-domain-containing and V-type proton ATPase proteins. Through our comparative transcriptomic approach using field reared individuals and co-expression network analysis we have also been able to identify a network of genes that change in expression in response to infection. These combined analyses provide evidence for a conserved response to P. marinus infections across infection intensities and suggest that DNA methylation may not be a reliable predictor of differential gene expression in long-term infections

A Shell-Neutral Modeling Approach Yields Sustainable Oyster Harvest Estimates: A Retrospective Analysis of the Louisiana State Primary Seed Grounds

A numerical model is presented that defines a sustainability criterion as no net loss of shell, and calculates a sustainable harvest of seed (\u3c75 mm) and sack or market oysters (\u3e= 75 mm). Stock assessments of the Primary State Seed Grounds conducted east of the Mississippi from 2009 to 2011 show a general trend toward decreasing abundance of sack and seed oysters. Retrospective simulations provide estimates of annual sustainable harvests. Comparisons of simulated sustainable harvests with actual harvests show a trend toward unsustainable harvests toward the end of the time series. Stock assessments combined with shell-neutral models can be used to estimate sustainable harvest and manage cultch through shell planting when actual harvest exceeds sustainable harvest. For exclusive restoration efforts (no fishing allowed), the model provides a metric for restoration success namely, shell accretion. Oyster fisheries that remove shell versus reef restorations that promote shell accretion, although divergent in their goals, are convergent in their management; both require vigilant attention to shell budgets