title: Endogeic earthworms shape bacterial functional communities and affect organic matter mineralization in a tropical soil.
abstract: Priming effect (PE) is defined as a stimulation of the mineralization of soil organic matter (SOM) following a supply of fresh organic matter. This process can have important consequences on the fate of SOM and on the management of residues in agricultural soils, especially in tropical regions where soil fertility is essentially based on the management of organic matter. Earthworms are ecosystem engineers known to affect the dynamics of SOM. Endogeic earthworms ingest large amounts of soil and assimilate a part of organic matter it contains. During gut transit, microorganisms are transported to new substrates and their activity is stimulated by (i) the production of readily assimilable organic matter (mucus) and (ii) the possible presence of fresh organic residues in the ingested soil. The objective of our study was to see (i) whether earthworms impact the PE intensity when a fresh residue is added to a tropical soil and (ii) whether this impact is linked to a stimulation/inhibition of bacterial taxa, and which taxa are affected. A tropical soil from Madagascar was incubated in the laboratory, with a (13)C wheat straw residue, in the presence or absence of a peregrine endogeic tropical earthworm, Pontoscolex corethrurus. Emissions of (12)CO(2) and (13)CO(2) were followed during 16 days. The coupling between DNA-SIP (stable isotope probing) and pyrosequencing showed that stimulation of both the mineralization of wheat residues and the PE can be linked to the stimulation of several groups especially belonging to the Bacteroidetes phylum.
authors.affiliation: Institut de Recherche pour le Développement, UMR Eco&Sols, Montpellier Cedex, France.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Bernard
authors.forename: Lydie
authors.initials: L
authors.lastname: Chapuis-Lardy
authors.forename: Tantely
authors.initials: T
authors.lastname: Razafimbelo
authors.forename: Malalatiana
authors.initials: M
authors.lastname: Razafindrakoto
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Pablo
authors.forename: Elvire
authors.initials: E
authors.lastname: Legname
authors.forename: Julie
authors.initials: J
authors.lastname: Poulain
authors.forename: Thomas
authors.initials: T
authors.lastname: Brüls
authors.forename: Michael
authors.initials: M
authors.lastname: O'Donohue
authors.forename: Alain
authors.initials: A
authors.lastname: Brauman
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Chotte
authors.forename: Eric
authors.initials: E
authors.lastname: Blanchart
mesh_terms: D000383:Agriculture; D000818:Animals; D001419:Bacteria / Q000145:classification*; D017753:Ecosystem; D008270:Madagascar; D008969:Molecular Sequence Data; D009835:Oligochaeta / Q000502:physiology*; D012988:Soil Microbiology; D014908:Triticum