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International audience; Environmental genomics and more generally omics, have influenced the paradigm of microbes response to toxics and pollutants and the understanding of who is affected and how this happens.Nanomaterials are promising nano-scaled objects that have revolutionized the technology and enabled the marketing of a dizzying number of products, routinely used by consumers. The nano-size feature endows these materials with properties that are different from their non-nano counterparts, allowing major innovation in technology. Besides, the nano-size aspect promotes interactions at the cellular and macromolecular level, with potential consequences. A tiny alteration in nanomaterial design (size, shape, surface charge, coating or functionalization, aggregation trend…) can upset their toxicological profile and the interaction with biological systems. The nanomaterials that are released by the use of nano-enabled products and technologies, end their life-cycle in all environmental compartments, air, water, soil, sediments, including humans. This worrying spreading together with their potential biological impacts, rate them as emerging contaminants.Recognizing that innovation in technology is needed and even inevitable, we used DNA metabarcoding and metabolomics not to expose the toxicity and the environmental impact of nanomaterials on bacteria, but to contribute to a safer and eco-design approach of these objects. Safety considerations, since the design first steps and during the entire life-cycle of new-generation nanomaterials, is one of the challenges of the Labex SERENADE. We aim to contribute to design nanomaterials with a reduced environmental impact over their life-cycle, on a plant-bacteria-soil model. For that purpose, we took advantage of the versatile profile of nanomaterials to modulate their interactions with biological systems, by using microbial enzymatic activities, and omics (metabarcoding and metabolomics) to examine the impact of particle size, coating, and inherent activity behaviour towards terrestrial ecosystems.How nanomaterials shaped the bacterial community in the unplanted soil, the rhizosphere and plant roots was considered by focusing on the core consortia of these compartments. The communication will emphasis on cerium oxide nanomaterials, as an example of safer-by-design approach.This work is a contribution to the Labex Serenade (ANR-11-LABX-0064) funded by the “Investissements d’Avenir” French Government program of the French National Research Agency (ANR) through the A*MIDEX project (ANR-11-IDEX-0001-02).

A large collection of bacterial strains, immunotrapped from soil and from the wheat rhizoplane, was subjected to polyphasic taxonomy by examining various pheno- and genotypic parameters. Strains were grouped on (inter) repetitive extragenic palindromic DNA (REP) PCR profiles at the intraspecies level. Pheno- and genotypic characters were assessed for representatives from 13 different REP groups. Strains of nine REP groups constituting two physiological BIOLOG clusters fell in the coherent DNA-DNA reassociation group of Ochrobactrum anthropi. Strains of two REP groups constituting a separate BIOLOG cluster fell in the coherent DNA-DNA reassociation group of Ochrobactrum intermedium. Additional phenotypic characters differentiating O. anthropi and O. intermedium were found. REP group K strains constituted a different BIOLOG cluster, a separate DNA-DNA reassociation group and a distinct phylogenetic lineage in 165 rDNA homology analysis, indicating that REP group K strains represent a new species. Diagnostic phenotypic characters were found. Closest relatives were Ochrobactrum species. The name Ochrobactrum grignonense sp. nov. is proposed (type strain OgA9aT = LMG 18954T = DSM 13338T). REP group J strains again constituted a different BIOLOG cluster, a separate DNA-DNA reassociation group and showed, as a biological particularity, a strict preference for the rhizoplane as habitat. Diagnostic phenotypic characters were found. This indicated that REP group J strains represent a further new species, although phylogenetic analyses using 16S rDNA homology were not able to separate the cluster of REP group J sequences significantly from 16S rDNA sequences of Ochrobactrum anthropi. The name Ochrobactrum tritici sp. nov. is proposed (type strain SCII24T = LMG 18957T = DSM 13340T).

chap. 7 *INRA, Centre de Dijon URD BP 86510 21065 Dijon cedex (FRA) Diffusion du document : INRA, Centre de Dijon URD BP 86510 21065 Dijon cedex (FRA); National audience

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Résumé*INRA, Centre de Nancy, Equipe Pathologie Forestière, 54280 Champenoux, FRANCE Diffusion du document : INRA, Centre de Nancy, Equipe Pathologie Forestière, 54280 Champenoux, FRANCE; National audience

International audience

International audience