Microbial communities are drivers of ecosystem functions throughout the planet, including in soils. The importance of biotic interactions between microorganisms for community assembly and composition, however, remains unclear. To find out, a recent study analyzed what happened when specific microbial taxa were depleted from soil samples from Northern France. Researchers systematically depleted soils using 18 taxa-specific anti-microbial treatments such as antibiotics and fungicides. This, the team believed, would create a vacuum in community structure, which competitor taxa would then be free to fill—if any such competitors existed. And that’s precisely what metagenomics revealed for prokaryotes in soil samples. 47.6% of dominant taxa received a significant boost in fitness following depletion. To establish a causative relationship between the depletion of some taxa and the increased relative abundance of others, the authors performed a targeted coalescence experiment by mixing depleted and non-manipulated microbial communities. After 45 days, 77% of the affected bacterial taxa no longer exhibited a difference in relative fitness in the coalescence treatments. Two main conclusions can be drawn from these results: (1) biotic interactions between microorganisms are playing a key role in the assembly of the soil microbiome, and (2) mixing depleted and non-manipulated communities reestablished the original interactions and at least partly restored both microbial community diversity and functions, offering new avenues for the restoration of damaged soil ecosystems by steering microbial communities.