The rhizosphere bacterial community is mainly regulated by plant species and soil type. Nematodes, the most abundant fauna in the rhizosphere, may impact rhizosphere bacteria either via top-down (bacterivores) or bottom-up (herbivores and bacterivores) regulation. However, the complex trophic control of herbivorous and bacterivorous nematodes on the rhizosphere bacterial community remains largely unexplored. Here, we investigate the separate and combined influence of bacterivorous and herbivorous nematodes ( Poikilolaimus oxycercus and Pratylenchus zeae) on the abundance, diversity and activity of the rhizosphere bacterial community of Italian ryegrass ( Lolium multiflorum), and whether root phenotypic plasticity mediates these effects. Our results show that both bacterivorous and herbivorous nematodes changed root traits, particularly root mass density and root C:N ratio, which in turn mediated their effect on rhizosphere chemistry (e.g. pH and DOC). Bacterivorous nematodes had both a direct negative effect on bacterial abundance, but they also exerted an indirect positive effect, by increasing root mass density and root C:N ratio, resulting in a negative overall effect. The presence of bacterivorous nematodes, either alone or in combination with herbivorous nematodes, led to different compositions of the rhizosphere bacterial community. Both root traits and rhizosphere chemistry contributed to explaining variations in bacterial community composition, with rhizosphere chemistry accounting for a larger portion of the variation, though the majority remained unexplained. We conclude that mass density and C:N ratio of the root system are key factors mediating the trophic control of bacterivorous and herbivorous nematodes on rhizosphere bacterial community, especially their abundance and activity. Given the high variation in bacterial community composition and the heterogenous nature of root systems, our results suggest the need for investigations at finer scales to understand the effects of root traits on rhizosphere bacterial community, and more generally how root plasticity mediates trophic interactions in the rhizosphere.