Shaping of Microbial Community Structure and Function in the Rhizosphere by Four Diverse Plant Species

International audienceUp to 20% of the carbon capital fixed by plants through photosynthesis is invested belowground as root exudates. The amount and composition of root exudates vary between plant species, and thus their influence on microbial community structure in the rhizosphere is also presumed to differ. The rhizosphere is a dynamic ecosystem where turnover is enhanced for fresh carbon from root exudates and ancient carbon from soil organic matter (SOM). Here, carbon dynamics were determined in the rhizosphere of four plant species: wheat, maize, rape, and barrel clover (Medicago truncatula). Bacterial communities that assimilated the different carbon sources were identified by DNA‐SIP (stable isotope probing), and bacterial populations were characterized by denaturing gradient gel electrophoresis (DGGE) analysis. This study provides evidence that different plant species can select different bacterial communities on their root tissues; however, bacterial communities inhabiting the rhizosphere soil of the four plant species were observed to be less different. The contribution of the rhizosphere to the carbon dynamics in soils was demonstrated by the stimulation of bacterial populations that assimilate carbon derived from root exudates, as well as the stimulation of populations involved in SOM degradation. This study illustrates that the plant host and its corresponding root exudates shape the soil bacterial community structure in the rhizosphere