Density, structure, and diversity of the cultivable arylsulfatase-producing bacterial community in the rhizosphere of field-grown rape and barley

In this study we investigated the arylsulfatase-producing bacterial community (ARS-BC) in the rhizosphere soils of field-grown rape in comparison with that of barley. For this, the rhizosphere soils from both plant species were sampled four times during plant growth. Soil arylsulfatase (ARS) activity and the density and the structure of the cultivable ARS-BC on M9-Xsulf medium were then determined. ARS activity in rape rhizosphere was greater than in barley rhizosphere and evolved along the phenology in the two rhizosphere soils. in parallel, the average density of ARS-BC in the rape rhizosphere was higher than that in the barley rhizosphere. Moreover, ARS activity is correlated with ARS-BC density both in rape and barley rhizosphere soils. The structure of the ARS-BC in the rape rhizosphere was different from that in the barley rhizosphere. In the rape rhizosphere, the ARS-BC was substantially more structured than in the barley rhizosphere. Among the ARS-BC, Actinobacteria and Pseudomonads were significantly present in the both rhizosphere soils. Actinobacteria predominated in the barley rhizosphere while Pseudomonads were mostly represented under rape. It is possible that the differences in ARS activity observed between rape and barley can be attributed to a different ARS-BC size and/or a different ARS-BC structure under these two plant covers. This impact of rape may be connected to a selective effect of rhizodeposits released by rape roots to the functional bacterial community. Our findings suggest that plant species, via their rhizodeposits, may affect the functional bacterial community and thus influence the dynamic of S in soil. (C) 2009 Elsevier Ltd. All rights reserved.