The mycoheterotrophic plant Monotropa uniflora relies on fungal symbionts for carbon and nutrient acquisition. However, its interactions with other microbial groups, beyond ectomycorrhizal fungi, remain unexplored. Here, we characterized bacterial and fungal communities associated with M. uniflora across two compartments: ectomycorrhizospheric soil linked to the mycorrhizal network and the surface-sterilized lower stem endosphere. Microbial community composition was assessed using high-throughput amplicon sequencing of the bacterial 16S rRNA gene and the fungal ITS region. Fungal richness was consistently higher in ectomycorrhizospheric soil than in the stem endosphere, whereas bacterial alpha diversity showed no consistent differences between compartments. Multivariate analyses suggested compartment-associated patterns in both bacterial and fungal community composition. Ectomycorrhizospheric soil was dominated by saprotrophic fungal taxa and bacterial groups with predicted metabolic potential, including taxa associated with iron, sulfur and nitrogen cycling. In contrast, the lower stem endosphere was enriched in bacterial taxa commonly associated with anaerobic and nitrogen-related metabolisms. Functional predictions further suggested an increase of carbon fixation-related pathways in rhizosphere-associated bacterial communities. Together, these results indicate that M. uniflora is associated with distinct and structured microbial assemblages across soil and internal plant compartments, highlighting the predicted functional potential of bacterial communities in nutrient- and carbon-related processes in mycoheterotrophic plant–soil systems alongside fungal partners.
Núñez-Muñoz et al. (Wed,) studied this question.