Soil microbial communities play key roles in ecosystem functioning. Yet, little is known about the importance of microbe-microbe interactions in soil microbial community assembly and functions. To address this knowledge gap, the objective of my thesis is to assess the role of interactions between micro-organisms in soil microbial communities. For this purpose, we will manipulate the interactions between microorganisms within complex soil microbial communities by (i) removing different members of the soil community, (ii) adding microbial taxa to the soil community and (iii) increasing the physical distance between members of the soil community. How shifts in microbial interactions affect community assembly will be determined after recolonization of sterile soil microcosms by the inoculated communities during several weeks. The resulting communities will be analyzed by 16S rRNA and 18S rRNA metabarcoding and bioinformatics tools such as network inference to identify the interacting community members. The consequences on community functions will be assessed for C and N cycles. This thesis project should allow unravelling soil microbial community assembly rules and the assessment of community manipulation impact on soil functions, therefore paving the way to steer soil microbial communities in agroecosystems.