Impact des intrants organiques et des conduites culturales sur la biomasse microbienne et la diversité des bactéries telluriques

L'objectif de ce travail est d'analyser, au cours d'une cinétique de 24 mois, les effets de différents types de produits organiques (Boue de STEP, Fumier, Compost de fumier et Compost de boue) sur les communautés microbiennes telluriques, en tenant compte des conduites culturales. Les communautés ont été analysées d'un point de vue quantitatif (dénombrement des bactéries hétérotrophes aérobies cultivables, quantification de l'ADN et du carbone microbien) et par un suivi de l'activité métabolique potentielle (Biolog) et de la diversité génétique (T-RFLP ADNr 16S). Nous avons mis en évidence un impact spécifique transitoire au cours des trois premiers mois suivant l'épandage. L'évolution des communautés semble particulièrement influencée par la proportion de carbone minéralisable et de lignine (Van Soest) dans les produits organiques. L'influence du labour et des végétaux implantés est également révélée par l'évolution de la structure des communautés bactériennes au cours de la cinétique.The aim of this work is to analyse the effects of four different organic products (turkey manure, compost of turkey manure and ligneous wastes, sewage sludge and compost of sewage sludge) on soil microbial communities in function of agricultural managements, during a 24 months kinetic. The microbial communities were characterised in a quantitative point of view (enumeration of heterotrophic cultivable bacteria, assay of soil total, microbial carbon assay) and in a qualitative one by potential metabolic fingerprinting (Biolog) and genetic structure of soil bacterial communities (T-RFLP 16S rDNA). A transitory impact specific to the different organic products was shown. The impact of organic products on microbial biomass and on bacterial community structure seemed to depend on their rate of lignin (Van Soest) and of mineralisable carbon. The influence of the tillage and the vegetation was revealed by the evolution of bacterial community structure during the 24 months of the experiments.ROUEN-BU Sciences (764512102) / SudocSudocFranceF

Détection et quantification d'Aphanomyces euteiches dans les parcelles agricoles pour la prévention des risques phytosanitaires

ROUEN-BU Sciences Madrillet (765752101) / SudocSudocFranceF

OprF polymorphism as a marker of ecological niche in Pseudomonas

OprF is the major outer-membrane protein of Pseudomonas sensu stricto (rRNA group I). In addition to playing a role as porin, membrane structural protein and root adhesion, this pleiotropic protein shows a length polymorphism corresponding to two types of OprF, termed OprF type 1 and OprF type 2. In a previous work, all the P. fluorescens isolated from bulk soil (non-rhizospheric) were shown to possess oprF type 1, while all the clinical P. fluorescens isolates and most rhizospheric strains corresponded to type 2. In this study, we further investigated the relation between the OprF polymorphism and the ecological niche by developing a culture-independent approach (a ratio polymerase chain reaction) to measure the percentage of each oprF type in environmental DNA samples, including two different soils and three different cultured plants (flax, wheat and grassland). Although the proportions of oprF type 2 between rhizospheric samples were quite variable, they were always very significantly higher (P95%) corresponded to type 1. We discuss the potential applications of this ecological fingerprint in an agronomic and taxonomic point of view

Elaboration et validation d’un indice d’état biologique des sols

Elaboration et validation d’un indice d’état biologique des sols. 9èmes Journées Nationales de l’Etude des Sol

Evolution de la structure des communautés microbiennes telluriques sour l’effet de contraintes anthropiques

Evolution de la structure des communautés microbiennes telluriques sour l’effet de contraintes anthropiques. 3ème édition du colloque d’Ecologie Microbienne de l’Association Francophone d’Ecologie Microbienn

Evolution de la structure des communautés microbiennes telluriques sour l’effet de contraintes anthropiques

Evolution de la structure des communautés microbiennes telluriques sour l’effet de contraintes anthropiques. 3ème édition du colloque d’Ecologie Microbienne de l’Association Francophone d’Ecologie Microbienn

Cycloclasticus spp. but also Pseudomonas spp. as PAH degrading bacteria in the Seine estuary (France)

International audienc

Cycloclasticus spp. but also Pseudomonas spp. as PAH degrading bacteria in the Seine estuary (France)

International audienc

A long-branch attraction artifact reveals an adaptive radiation in Pseudomonas

A significant proportion of protein-encoding gene phylogenies in bacteria is inconsistent with the species phylogeny. It was usually argued that such inconsistencies resulted from lateral transfers. Here, by further studying the phylogeny of the oprF gene encoding the major surface protein in the bacterial Pseudomonas genus, we found that the incongruent tree topology observed results from a long-branch attraction (LBA) artifact and not from lateral transfers. LBA in the oprF phylogeny could be explained by the faster evolution in a lineage adapted to the rhizosphere, highlighting an unexpected adaptive radiation. We argue that analysis of such artifacts in other inconsistent bacterial phylogenies could be a valuable tool in molecular ecology to highlight cryptic adaptive radiations in microorganisms