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Rhizosphere effect is stronger than PAH concentration on shaping spatial bacterial assemblages along centimetre-scale depth gradients.

Authors
  • Bourceret, Amélia1, 2
  • Leyval, Corinne1, 2
  • Thomas, François1, 2
  • Cébron, Aurélie1, 2
  • 1 a CNRS, LIEC UMR7360, Faculté des Sciences et Technologies, boulevard des Aiguillettes, B.P. 70239, 54506 Vandoeuvre-lès-Nancy, France. , (France)
  • 2 b Université de Lorraine, LIEC UMR7360, Faculté des Sciences et Technologies, boulevard des Aiguillettes, B.P. 70239, 54506 Vandoeuvre-lès-Nancy, France. , (France)
Type
Published Article
Journal
Canadian Journal of Microbiology
Publisher
Canadian Science Publishing
Publication Date
Nov 01, 2017
Volume
63
Issue
11
Pages
881–893
Identifiers
DOI: 10.1139/cjm-2017-0124
PMID: 28841396
Source
Medline
Keywords
License
Unknown

Abstract

At centimetre scale, soil bacterial assemblages are shaped by both abiotic (edaphic characteristics and pollutants) and biotic parameters. In a rhizobox experiment carried out on planted industrial soil contaminated with polycyclic aromatic hydrocarbons (PAHs), we previously showed that pollution was distributed randomly with hot and cold spots. Therefore, in the present study, we investigated the effect of this patchy PAH distribution on the bacterial community assemblage and compared it with that of root depth gradients found in the rhizosphere of either alfalfa or ryegrass. Sequencing of 16S rRNA amplicons revealed a higher bacterial diversity in ryegrass rhizosphere and enrichment in specific taxa by the 2 plant species. Indeed, Bacteroidetes, Firmicutes, and Gammaproteobacteria were globally favored in alfalfa, whereas Acidimicrobiia, Chloroflexi, Alpha-, and Betaproteobacteria were globally favored in ryegrass rhizosphere. The presence of alfalfa created depth gradients of root biomass, carbohydrate, and pH, and actually shaped the bacterial assemblage, favoring Actinobacteria near the surface and Gemmatimonadetes and Proteobacteria at greater depths. Contrarily, the bacterial assemblage was homogeneous all along depths of the ryegrass root system. With both plant species, the PAH content and random distribution had no significant effect on bacterial assemblage. Globally, at centimeter scale, bacterial community assemblages were mostly shaped by soil physical and chemical depth gradients induced by root growth but not by patchy PAH content.

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