Unraveling biotic interactions determining soil microbial community assembly and functioning

Microbial communities are at the heart of all ecosystems and yet a sound understanding of the ecological processes governing the assembly these communities is missing. To address the role of biotic interactions in the assembly and functioning of the soil microbiota, we used a top down manipulation approach based on the removal of various populations in a natural soil microbial community. We hypothesized that if biotic interactions are the shaping microbiota assembly, then removal of microbial groups should largely affect the fitness the remaining ones during soil recolonization. We show that about 49% of the dominant bacterial taxa were competing, underlining the importance of biotic interactions in the assembly of microbial community in soil. Moreover, evidence for competitive exclusion between members of Bacillales and Proteobacteriales suggests that simple rules of microbial community assembly can be identified. Our findings also indicate stronger changes in the activities related to N- than to C-cycling in response to shifts in microbial community assembly