Nematode grazing increases the allocation of plant-derived carbon to soil bacteria and saprophytic fungi, and activates bacterial species of the rhizosphere

•SIP (13CO2 and 18O water) revealed impacts of soil fauna on microbial functioning.•Nematode grazing increased net assimilation of plant derived C in microbial biomass.•Bacterivore nematodes impacted directly bacteria and indirectly saprophytic fungi.•Grazing activated bacterial taxa typical for the rhizosphere microbiome.•Grazing enhances allocation of plant C and thus energy to the soil food web.