Search results for "communitie"

Prévalence de pathogènes humains dans les sols français, effet des facteurs pédoclimatiques, biologiques et du mode d'utilisation des sols

2013

Soil contamination by bacterial pathogens can occur through manure, sewage sludge spreading or irrigation using waste water treatment plants effluents. Agricultural soils may act as reservoirs for these pathogens, play a significant role in their dissemination, leading to the potential contamination of food and water resources. Health risk associated with the occurrence of pathogens in environmental matrices has to be thoroughly evaluated. In this context, the objectives of this work were: i) to determine the prevalence of two pathogenic bacterial species (Listeria monocytogenes and Enterococcus faecalis) in a large collection of French soils originated from a systematic soil survey of the …

Biogeographical patterns of soil bacterial communities.

2009

International audience; This study provides the first maps of variations in bacterial community structure on a broad scale based on genotyping of DNA extracts from 593 soils from four different regions of France (North, Brittany, South-East and Landes). Soils were obtained from the soil library of RMQS (Réseau de Mesures de la Qualité des Sols = French soil quality monitoring network). The relevance of a biogeographic approach for studying bacterial communities was demonstrated by the great variability in community structure and specific geographical patterns within and between the four regions. The data indicated that the distribution of bacterial community composition might be more relate…

Weed communities in conservation agriculture: what really changes?

2022

Conservation agriculture (CA) has been identified as one of the farming systems likely to deliver sustainable agriculture but its effects over time on the diversity and composition of weed communities are still discussed. For ten years, different studies were carried out in in East of France in cropping system with short rotations essentially composed with winter crops. The objective of these different studies was to identify, focusing on the transition period, the changes in the composition of communities and the consequences in terms of agronomic risk in CA systems. Using networks of 100 winter wheat fields selected to encompass a gradient of years in CA (1 to 20 years), the changes that …

Microalgae community structure analysis based on 18S rDNA amplification from DNA extracted directly from soil as a potential soil bioindicator

2005

International audience; Soil algae are photosynthetically active microorganisms showing changeable community structure, depending on the soil type, the agricultural practices and the application of pesticides. To characterise algal community structure, molecular approaches complementary to classical microbiological approaches based on the isolation and the culture of soil algae are required. Our study describes a polymerase chain reaction (PCR) approach targeting algal 18S rDNA sequences of desoxyribonucleic acid (DNA) samples extracted either from unialgal eukaryotic microalgae culture, complex assemblages of microalgae populations or natural soil communities. Our first results showed that…

Biogeography of soil microbial communities: a review and a description of the ongoing french national initiative

2010

International audience; Microbial biogeography is the study of the distribution of microbial diversity on large scales of space and time. This science aims at understanding biodiversity regulation and its link with ecosystem biological functioning, goods and services such as maintenance of productivity, of soil and atmospheric quality, and of soil health. Although the initial concept dates from the early 20th century (Beijerinck (1913) De infusies en de ontdekking der backterien, in: Jaarboek van de Knoniklijke Akademie van Wetenschappen, Muller, Amsterdam), only recently have an increasing number of studies have investigated the biogeographical patterns of soil microbial diversity. A such …

DIAGSOL : development of a new functional marker of exposure to herbicides B-triketones in an agricultural soil

2020

Numerous herbicides target an enzyme found not only in weeds but also in « non-target organisms » such as microorganisms. This proof-of-concept study aims to use microbial gene encoding the targeted enzyme or the targeted enzyme itself as a marker for herbicide exposure in soils. The hppd gene and the encoded enzyme (HPPD; 4-hydroxyphenylpyruvate dioxygenase), targeted by B-triketone herbicides, are the subject of this study. In silico analyses reveal that the hppd gene is spread out in all bacterial phyla. Primers specific to this gene were designed. This primer pair is used to measure the abundance, the composition and the diversity of the hppd bacterial community in soil microcosms expos…

Distribution and determinism of abundance, diversity and structure of microbial communities at different spatial scales to support agricultural devel…

2018

Les propriétés des sols déterminent notre capacité à produire des biens et des services en quantité et en qualité. Dans ce contexte, la composante microbienne des sols occupe une place prépondérante de part son abondance et son extrême diversité : on estime qu’un gramme de sol contient 109 bactéries et 105 champignons, pour environ 106 espèces bactériennes et 103 à 104 espèces de champignons. Cette diversité taxonomique des microorganismes du sol supporte une extraordinaire diversité fonctionnelle qui leur confère un rôle déterminant dans le fonctionnement du sol tant qualitativement (cycles biogéochimiques, structure du sol ; dégradation des composés exogènes, régulation biologique) que qu…

Plant genotype: a lever in the interactions between plant and its associated rhizosphere microbiome

2018

International audience; In the context of highly pressured agricultural production using low levels of inputs, cropping strategies could take advantage of existing plant-microbiome interactions that can improve both plant growth and health. We believe that plant genetics can provide some clues to better understand the mechanisms underlying microbiome recruitment by the plant.The aims of this work were (i) to assess plant genotype effect on the rhizosphere bacterial communities in relation to the plant nutritional strategies for a core collection of 155 genotypes of Medicago truncatula and (ii) to highlight the genetic determinisms potentially associated in these interactions. To achieve the…

Multiple-scale distribution and function of soil microorganisms

2011

Nitrous oxide production in the terrestrial environment

2011

Chapitre : 11; Terrestrial ecosystems are a major source of nitrous oxide (N2O), with soils accounting for ~70% of the atmospheric loading of this greenhouse gas. Here we provide a synthesis of current understanding of the environmental regulation of N2O production and reduction through different microbial pathways, presenting examples of where measured emissions have been related to characterizations of the underpinning microbial communities. We explore the direct and indirect influence of plants on rhizosphere N2O production, reduction and net emission, and the interactions between N2O production and methane oxidation, as examples of coupling between the C and N cycles that need to be con…