Assessment of the global toxicity of marine sediments from the Dakar peninsula (Senegal, West Africa).

Marine pollution in West Africa is major threat particularly around coastal megacities. We assess the chemical and ecotoxicological quality of the marine sediments in various submerged sampling sites of Dakar. Analysis revealed that sediments were slightly basic in which fine and coarse sands predominated. High percentages of total organic carbon were found sometime above 6%. Higher levels of heavy metal were reported than in previous studies. Chromium and nickel were above the Probable Effect Concentration. Low trophic level appeared not affected by the overall toxicity, while medium trophic level was more affected. Indeed, the vast majority (91%) of sites studied revealed a net percentage of Magallana gigas embryolarval developmental abnormality over 20%. The assessment of the global toxicity of marine sediments from the Dakar sites Studied (n = 11) seemed, almost, as a whole, to be in a poor ecotoxicological state calling to take measures to improve the sanitary condition of this marine feature.

Quantification of soil organic carbon stock in urban soils using visible and near infrared reflectance spectroscopy (VNIRS) in situ or in laboratory conditions.

Urban soils, like other soils, can be sink or source for atmospheric carbon dioxide, and due to urban expansion, are receiving increasing attention. Studying their highly variable attributes requires high-density sampling, which can hardly be achieved using conventional approaches. The objective of this work was to determine the ability of visible and near infrared reflectance spectroscopy (VNIRS) to quantify soil organic carbon (SOC) concentration (gC kg-1) and stock (gC dm-3, or MgC ha-1 for a given depth layer) in parks and sealed soils of two French cities, Marseille and Nantes, using spectra collected on pit walls or in laboratory conditions (air dried, 2 mm sieved samples). Better VNIRS predictions were achieved using laboratory than in situ spectra (R2 ≈ 0.8-0.9 vs. 0.7-0.8 in validation), and for sample SOC concentration than stock (R2val up to 0.83 in situ and 0.95 in the laboratory vs. 0.78 and 0.89, respectively). Stock was conventionally calculated according to four methods that variably account for coarse particles (>2 mm); and it was better predicted when coarse particles were not taken into account. This was logical using laboratory spectra, collected on 2 mm sieved samples; but concerning in situ spectra, this suggested the operator tended to put the spectrometer beside the coarsest particles during spectrum acquisition. This point is worth considering for urban soils, often rich in coarse particles. Stocks were then aggregated at the profile level: SOC stock prediction was more accurate at profile than sample level when using laboratory spectra (R2val = 0.94 vs. 0.89, respectively), probably due to uncertainty compensation; but this was not the case when using in situ spectra, possibly because samples collected for SOC analysis and corresponding VNIRS scans were not at the exact same location. This work demonstrates VNIRS usefulness for quantifying SOC stock time- and cost-effectively, in urban soils especially.

Recovery of symbiotic nitrogen fixing acacia rhizobia from Merzouga Desert sand dunes in South East Morocco--Identification of a probable new species of Ensifer adapted to stressed environments.

Bacteria capable of nodulating Acacia tortilis and A. gummifera could be recovered from sand dunes collected in the Moroccan Merzouga desert. The trapping approach enabled the recovery of 17 desert rhizobia that all clustered within the Ensifer (Sinorhizobium) genus. Four isolates of the dominant genotype comprising 15 strains as well as 2 divergent strains were further characterized by MLSA. Phylogenetic analyzes indicated that the dominant genetic type was belonging to a new and yet undefined species within the Ensifer genus. Interestingly, housekeeping gene phylogenies showed that this possibly new species is also present in another desert but in India. Phylogenetic analyses of nifH and nodC sequences showed high sequence conservation among the Moroccan strains belonging to the dominant genotype but high divergence with sequences from Indian isolates suggesting acquisition of symbiotic genes through Horizontal Gene Transfer. These desert rhizobia were capable of growing in media containing high salt concentrations, under high pH and most of the strains showed growth at 45°C. Only recovered from desert type of Biome, yet, this new taxon appears particularly adapted to such harsh environment.

Transcriptome Changes in Hirschfeldia incana in Response to Lead Exposure.

Hirschfeldia incana, a pseudometallophyte belonging to the Brassicaceae family and widespread in the Mediterranean region, was selected for its ability to grow on soils contaminated by lead (Pb). The global comparison of gene expression using microarrays between a plant susceptible to Pb (Arabidopsis thaliana) and a Pb tolerant plant (H. incana) enabled the identification of a set of specific genes expressed in response to lead exposure. Three groups of genes were particularly over-represented by the Pb exposure in the biological processes categorized as photosynthesis, cell wall, and metal handling. Each of these gene groups was shown to be directly involved in tolerance or in protection mechanisms to the phytotoxicity associated with Pb. Among these genes, we demonstrated that MT2b, a metallothionein gene, was involved in lead accumulation, confirming the important role of metallothioneins in the accumulation and the distribution of Pb in leaves. On the other hand, several genes involved in biosynthesis of ABA were shown to be up-regulated in the roots and shoots of H. incana treated with Pb, suggesting that ABA-mediated signaling is a possible mechanism in response to Pb treatment in H. incana. This latest finding is an important research direction for future studies.

Lead tolerance and accumulation in Hirschfeldia incana, a Mediterranean Brassicaceae from metalliferous mine spoils.

Lead is a heavy metal of particular concern with respect to environmental quality and health. The lack of plant species that accumulate and tolerate Pb is a limiting factor to understand the molecular mechanisms involved in Pb tolerance. In this study we identified Hirschfeldia incana, a Brassicaceae collected from metalliferous mine spoils in Morocco, as a Pb accumulator plant. H. incana exhibited high Pb accumulation in mine soils and in hydroponic cultures. Major Pb accumulation occurred in the roots and a part of Pb translocated from the roots to the shoots, even to the siliques. These findings demonstrated that H. incana is a Pb accumulator species. The expression of several candidate genes after Pb-exposure was measured by quantitative PCR and two of them, HiHMA4 and HiMT2a, coding respectively for a P1B-type ATPase and a metallothionein, were particularly induced by Pb-exposure in both roots and leaves. The functional characterization of HiHMA4 and HiMT2a was achieved using Arabidopsis T-DNA insertional mutants. Pb content and primary root growth analysis confirmed the role of these two genes in Pb tolerance and accumulation. H. incana could be considered as a good experimental model to identify genes involved in lead tolerance and accumulation in plants.

Self-reported data: a major tool to assess compliance with anti-malarial combination therapy among children in Senegal.

BACKGROUND: Although there are many methods available for measuring compliance, there is no formal gold standard. Different techniques used to measure compliance were compared among children treated by the anti-malarial amodiaquine/sulphadoxine-pyrimethamine (AQ/SP) combination therapy, in use in Senegal between 2004 and 2006. METHODS: The study was carried out in 2004, in five health centres located in the Thies region (Senegal). Children who had AQ/SP prescribed for three and one day respectively at the health centre were recruited. The day following the theoretical last intake of AQ, venous blood, and urine samples were collected for anti-malarial drugs dosage. Caregivers and children above five years were interviewed concerning children's drug intake. RESULTS: Among the children, 64.7% adhered to 80% of the prescribed dose and only 37.7% were strict full adherent to the prescription. There was 72.7% agreement between self-reported data and blood drug dosage for amodiaquine treatment. Concerning SP, results found that blood dosages were 91.4% concordant with urine tests and 90% with self-reported data based on questionnaires. CONCLUSION: Self-reported data could provide useful quantitative information on drug intake and administration. Under strict methodological conditions this method, easy to implement, can be used to describe patients' behaviors and their use of new anti-malarial treatment. Self-reported data is a major tool for assessing compliance in resource poor countries. Blood and urine drug dosages provide qualitative results that confirm any drug intake. Urine assays for SP could be useful to obtain public health data, for example on chemoprophylaxis among pregnant women.