This study investigates the impact of plant species on the bacterial community structure in the rhizosphere, using stable isotope probing (SIP) to determine which bacterial communities assimilate root exudates and soil organic matter (SOM). Four plant species—wheat, maize, rape, and barrel clover—were grown in the same soil under 13CO₂ labeling. DNA from rhizosphere soil was fractionated by isopycnic centrifugation, and 13C-DNA was analyzed by denaturing gradient gel electrophoresis (DGGE) to identify bacteria assimilating root exudates and SOM. The results show that plant species significantly shaped the rhizosphere bacterial community structure. Bacteria related to Sphingobacteriales and Myxococcus assimilated root exudates in all four plants, while Sphingomonadales utilized both carbon sources and were specific to monocotyledons. Enterobacter and Rhizobiales colonized all compartments of all plants and used both fresh and ancient carbon, indicating a generalist role. The study also highlights the indirect impact of root exudates on SOM assimilation by a diverse bacterial community. Overall, the findings demonstrate that plant species influence the composition and function of rhizosphere bacterial communities through the release of root exudates and the selection of specific bacterial species.This study investigates the impact of plant species on the bacterial community structure in the rhizosphere, using stable isotope probing (SIP) to determine which bacterial communities assimilate root exudates and soil organic matter (SOM). Four plant species—wheat, maize, rape, and barrel clover—were grown in the same soil under 13CO₂ labeling. DNA from rhizosphere soil was fractionated by isopycnic centrifugation, and 13C-DNA was analyzed by denaturing gradient gel electrophoresis (DGGE) to identify bacteria assimilating root exudates and SOM. The results show that plant species significantly shaped the rhizosphere bacterial community structure. Bacteria related to Sphingobacteriales and Myxococcus assimilated root exudates in all four plants, while Sphingomonadales utilized both carbon sources and were specific to monocotyledons. Enterobacter and Rhizobiales colonized all compartments of all plants and used both fresh and ancient carbon, indicating a generalist role. The study also highlights the indirect impact of root exudates on SOM assimilation by a diverse bacterial community. Overall, the findings demonstrate that plant species influence the composition and function of rhizosphere bacterial communities through the release of root exudates and the selection of specific bacterial species.