Search results for " Hunger"
showing 10 items of 1330 documents
Shifts in size, genetic structure and activity of the soil denitrifier community by nematode grazing
2010
International audience; Bacterial-feeding nematodes represent an important driver of the soil microbial activity and diversity. This study aimed at characterizing the impact of nematode grazing on a model functional bacterial guild involved in N-cycling, the denitrifiers. Bacterial-feeding nematodes (Cephalobus pseudoparvus) were inoculated into soil microcosms whose indigenous nematofauna had previously been removed. The size, genetic structure and activity of the soil denitrifier community were characterized 15 and 45 days after nematodes inoculation using quantitative PCR of the nirK, nirS and nosZ denitrification genes, fingerprinting of the nirK and nirS genes and denitrification enzym…
Evidence for shifts in the structure and abundance of the microbial community in a long-term PCB-contaminated soil under bioremediation.
2011
International audience; Although the impact of bioremediation of PCB-contaminated sites on the indigenous microbial community is a key question for soil restoration, it remains poorly understood. Therefore, a small-scale bioremediation assay made of (a) a biostimulation treatment with carvone, soya lecithin and xylose and (b) two bioaugmentation treatments, one with a TSZ7 mixed culture and another with a Rhodococcus sp. Z6 pure strain was set up. Changes in the structure of the global soil microbial community and in the abundances of different taxonomic phyla were monitored using ribosomal intergenic spacer analysis (RISA) and real-time PCR. After an 18-month treatment, the structure of th…
Cassava starch processing at small scale in North Vietnam
2008
International audience; In Northern Vietnam, small-scale cassava starch processing is conducted in densely populated craft villages, where processors face difficulties to expand their activities. Three different processing systems were studied among a cluster of three communes in the Red River Delta, producing up to 430 t of starch (at 55% dry matter) per day. The first system, type A, is a cylindrical rasper and a manual sieve, the second, type B, is a cylindrical rasper and stirring-filtering machine and the third, type C, used equipment for both the rasping and filtering stages. Moisture, starch, crude fibers and ash content analysis were carried out on samples collected from the A-B-C m…
Mammal assemblage composition predicts global patterns in emerging infectious disease risk
2021
Abstract As a source of emerging infectious diseases, wildlife assemblages (and related spatial patterns) must be quantitatively assessed to help identify high‐risk locations. Previous assessments have largely focussed on the distributions of individual species; however, transmission dynamics are expected to depend on assemblage composition. Moreover, disease–diversity relationships have mainly been studied in the context of species loss, but assemblage composition and disease risk (e.g. infection prevalence in wildlife assemblages) can change without extinction. Based on the predicted distributions and abundances of 4466 mammal species, we estimated global patterns of disease risk through …
Mapping and determinism of soil microbial community distribution across an agricultural landscape.
2015
Article en open access; International audience; Despite the relevance of landscape, regarding the spatial patterning of microbial communities and the relative influence of environmental parameters versus human activities, few investigations have been conducted at this scale. Here, we used a systematic grid to characterize the distribution of soil microbial communities at 278 sites across a monitored agricultural landscape of 13km(2). Molecular microbial biomass was estimated by soil DNA recovery and bacterial diversity by 16S rRNA gene pyrosequencing. Geostatistics provided the first maps of microbial community at this scale and revealed a heterogeneous but spatially structured distribution…
Biogenic amines in fermented foods
2010
Food-fermenting lactic acid bacteria (LAB) are generally considered to be non-toxic and non-pathogenic. Some species of LAB, however, can produce biogenic amines (BAs). BAs are organic, basic, nitrogenous compounds, mainly formed through decarboxylation of amino acids. BAs are present in a wide range of foods, including dairy products, and can occasionally accumulate in high concentrations. The consumption of food containing large amounts of these amines can have toxicological consequences. Although there is no specific legislation regarding BA content in many fermented products, it is generally assumed that they should not be allowed to accumulate. The ability of microorganisms to decarbox…
Spatial distribution of N-cycling microbial communities showed complex patterns in constructed wetland sediments.
2013
International audience; Constructed wetlands are used for biological treatment of wastewater from agricultural lands carrying pollutants such as nitrates. Nitrogen removal in wetlands occurs from direct assimilation by plants and through microbial nitrification and denitrification. We investigated the spatial distribution of N-cycling microbial communities and genes involved in nitrification and denitrification in constructed wetland sediments receiving irrigation water. We used quantitative real-time PCR (qPCR) to characterize microbial communities. Geostatistical variance analysis was used to relate them with vegetation cover and biogeochemical sediment properties. The spatial distributio…
Novel virocell metabolic potential revealed in agricultural soils by virus-enriched soil metagenome analysis
2021
International audience; Viruses are now recognized as important players in microbial dynamics and biogeochemical cycles in the oceans. Yet, compared with aquatic ecosystems, virus discovery in terrestrial ecosystems has been challenging partly due to the inherent complexity of soils. To expand our understanding of soil viruses and their putative contributions to soil microbial processes, we analysed metagenomes of community-level virus-enriched suspensions by tangential flow filtration obtained from two French agricultural soils. We found viral sequences representing a total of 239 viral operational taxonomic units that corresponded to 29.5% of the mapping reads in the metagenomic datasets.…
Comparative genetic diversity of the narG, nosZ, and 16S rRNA genes in fluorescent Pseudomonads
2003
ABSTRACT The diversity of the membrane-bound nitrate reductase ( narG ) and nitrous oxide reductase ( nosZ ) genes in fluorescent pseudomonads isolated from soil and rhizosphere environments was characterized together with that of the 16S rRNA gene by a PCR-restriction fragment length polymorphism assay. Fragments of 1,008 bp and 1,433 bp were amplified via PCR with primers specific for the narG and nosZ genes, respectively. The presence of the narG and nosZ genes in the bacterial strains was confirmed by hybridization of the genomic DNA and the PCR products with the corresponding probes. The ability of the strains to either reduce nitrate or totally dissimilate nitrogen was assessed. Overa…
Long-term impact of 19 years' farmyard manure or sewage sludge application on the structure, diversity and density of the protocatechuate-degrading b…
2012
International audience; Impact of long-term biosolids application on soil-living micro-organisms key players of ecosystemic services is scarcely reported. Here, the impact of the 19 year-long application of farmyard manure (FM) and sewage sludge (SS) organic fertilisation regimes on the protocatechuate-degrading bacterial (pca) community was estimated by comparison to a mineral fertilisation regime (U). The structure, diversity and density of the pca community were determined using pcaH, a gene encoding the protocatechuate 3,4-dioxygenase. Ten years after the last application, the structure of the pca community in soils amended with 55100 (100 t/ha/2 years) and to a lesser extent with FM (1…