Search results for "SOIL MICROBIOLOGY"
showing 10 items of 213 documents
Sex-specific interaction between arbuscular mycorrhizal and dark septate fungi in the dioecious plant Antennaria dioica (Asteraceae).
2012
Male and female plants of dioecious species often differ in their resource demands and this has been linked to secondary sexual dimorphism, including sex-specific interactions with other organisms such as herbivores and pollinators. However, little is known about the interaction between dioecious plants and fungal root endophytes. Plants may be simultaneously colonised by arbuscular mycorrhizal (AM) and dark septate (DS) fungi. While it is well established that AM mutualism involves reciprocal transfer of photosynthates and mineral nutrients between roots of host plants and these fungi, the role of DS fungi remains controversial. Here, we report the temporal and spatial variation in AM and …
Diversity and Evolution of the Phenazine Biosynthesis Pathway
2010
ABSTRACT Phenazines are versatile secondary metabolites of bacterial origin that function in biological control of plant pathogens and contribute to the ecological fitness and pathogenicity of the producing strains. In this study, we employed a collection of 94 strains having various geographic, environmental, and clinical origins to study the distribution and evolution of phenazine genes in members of the genera Pseudomonas , Burkholderia , Pectobacterium , Brevibacterium , and Streptomyces . Our results confirmed the diversity of phenazine producers and revealed that most of them appear to be soil-dwelling and/or plant-associated species. Genome analyses and comparisons of phylogenies inf…
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…
Diuron mineralisation in a Mediterranean vineyard soil: impact of moisture content and temperature
2010
BACKGROUND: The diuron-mineralising ability of the microbiota of a Mediterranean vineyard soil exposed each year to this herbicide was measured. The impact of soil moisture and temperature on this microbial activity was assessed. RESULTS: The soil microbiota was shown to mineralise diuron. This mineralising activity was positively correlated with soil moisture content, being negligible at 5% and more than 30% at 20% soil moisture content. According to a double Gaussian model applied to fit the dataset, the optimum temperature/soil moisture conditions were 27.9 °C/19.3% for maximum mineralisation rate and 21.9 °C/18.3% for maximum percentage mineralisation. The impact of temperature and soil…
Biotic and abiotic soil properties influence survival of Listeria monocytogenes in soil
2013
International audience; Listeria monocytogenes is a food-borne pathogen responsible for the potentially fatal disease listeriosis and terrestrial ecosystems have been hypothesized to be its natural reservoir. Therefore, identifying the key edaphic factors that influence its survival in soil is critical. We measured the survival of L. monocytogenes in a set of 100 soil samples belonging to the French Soil Quality Monitoring Network. This soil collection is meant to be representative of the pedology and land use of the whole French territory. The population of L. monocytogenes in inoculated microcosms was enumerated by plate count after 7, 14 and 84 days of incubation. Analysis of survival pr…
A new species of Pythium with filamentous sporangia having pectinolytic activities, isolated in the Burgundy region of France.
2001
A new species, Pythium pectinolyticum (F-83.1), isolated from soil samples taken in the Burgundy region is being described here. This species is characterised by its filamentous non-inflated type of sporangia, smooth-walled mostly catenulate oogonia and very rare antheridia. This fungus is a very slow-growing organism on most of the solid media, but it grows well in liquid media and also on those containing pectin as the sole source of carbon. Morphological features are described here together with the sequences of the internal transcribed spacer 1 region of the nuclear ribosomal DNA of the fungus, its comparison with related species, and its pectinolytic behaviour.
Quantification of denitrifying bacteria in soils by nirK gene targeted real-time PCR.
2004
Abstract Denitrification, the reduction of nitrate to nitrous oxide or dinitrogen, is the major biological mechanism by which fixed nitrogen returns to the atmosphere from soil and water. Microorganisms capable of denitrification are widely distributed in the environment but little is known about their abundance since quantification is performed using fastidious and time-consuming MPN-based approaches. We used real-time PCR to quantify the denitrifying nitrite reductase gene (nirK), a key enzyme of the denitrifying pathway catalyzing the reduction of soluble nitrogen oxide to gaseous form. The real-time PCR assay was linear over 7 orders of magnitude and sensitive down to 102 copies by assa…
Genetic variability of Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) populations from Latin America is associated with variations in susceptib…
2006
ABSTRACT Bacillus thuringiensis strains isolated from Latin American soil samples that showed toxicity against three Spodoptera frugiperda populations from different geographical areas (Mexico, Colombia, and Brazil) were characterized on the basis of their insecticidal activity, crystal morphology, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of parasporal crystals, plasmid profiles, and cry gene content. We found that the different S. frugiperda populations display different susceptibilities to the selected B. thuringiensis strains and also to pure preparations of Cry1B, Cry1C, and Cry1D toxins. Binding assays performed with pure toxin demonstrated that the differences in the …
HONO Emissions from Soil Bacteria as a Major Source of Atmospheric Reactive Nitrogen
2013
From Soil to Sky Trace gases emitted either through the activity of microbial communities or from abiotic reactions in the soil influence atmospheric chemistry. In laboratory column experiments using several soil types, Oswald et al. (p. 1233 ) showed that soils from arid regions and farmlands can produce substantial quantities of nitric oxide (NO) and nitrous acid (HONO). Ammonia-oxidizing bacteria are the primary source of HONO at comparable levels to NO, thus serving as an important source of reactive nitrogen to the atmosphere.
Interaction between Medicago truncatula and Pseudomonas fluorescens: evaluation of costs and benefits across an elevated atmospheric CO2.
2012
10 pages; International audience; Soil microorganisms play a key role in both plants nutrition and health. Their relation with plant varies from mutualism to parasitism, according to the balance of costs and benefits for the two partners of the interaction. These interactions involved the liberation of plant organic compounds via rhizodeposition. Modification of atmospheric CO2 concentration may affect rhizodeposition and as a consequence trophic interactions that bind plants and microorganisms. Positive effect of elevated CO2 on plants are rather well known but consequences for micoorganisms and their interactions with plants are still poorly understood. A gnotobiotic system has been devel…