Microbial community composition of nest-carton and adjoining soil of the ant Lasius fuliginosus and the role of host secretions in structuring microbial communities

The ant Lasius fuliginosus stabilizes its carton-nest structures through the growth of fungi. Here we investigated the fungal and bacterial community composition in nest-carton and adjoining soil of L. fuliginosus. We found that fungal communities in the nest were stable and distinct from surrounding soil over 2 y, while bacterial communities were not stable with the differentiation between nest and surrounding soil changing over the years. This suggests that in contrast to bacterial communities, fungal communities in the nest are actively managed by the ant L. fuliginosus, a result that was corroborated by additional growth assays. In these assays we found that an antagonistic fungus was inhibited when incubated with extracts of ant body parts, while fungal associates were not only not affected but even partly favoured in their growth. Overall our results support a role of host secretions in shaping the association between L. fuliginosus and fungal partners