Bacterial communities in the potato tuberosphere share similarities with bulk soil and rhizosphere communities, yet possess distinct features

Abstract Background and Aims Bacterial communities in tuberospheres (soil attached to potato tubers) and levels of bacterial sulfur cycling in this compartment have been overlooked in healthy potato plants to date. Here, we aimed to describe the structure and composition of tuberosphere bacteriomes and its sulfur cycling capability using the rhizosphere and bulk soil bacterial community characteristics as a reference. Methods We collected rhizosphere and tuberosphere soil along with bulk soil from two field grown potato varieties with different properties. Bacterial communities were characterized by 16S rRNA gene amplicon sequencing. Bacterial sulfur cycling indicators were evaluated with cultivation dependent and independent methods and were correlated (Spearman) with the relative abundance of bacterial families. Results The structure of tuberosphere bacterial communities either overlapped with the bulk soil or had similarities with the rhizosphere. Relative abundance of specific bacterial families increased or decreased from bulk soil to tuberosphere and rhizosphere continuum. Tuberospheres had a tendency for higher arylsulfonate utilization compared to bulk soil. The families Sphindomonadaceae, Sphingobacteriaceae and Rhizobiaceae which presented a decline in their relative abundances from the rhizosphere to tuberosphere and bulk soil had positive correlations with sulfur cycling indicators. Conclusion Potato variety and soil characteristics played a role in structuring the tuberosphere bacterial communities. Tuberospheres represent a transitional environment between bulk soil and rhizosphere indicative from the intermediate relative abundances of specific bacterial families. A moderate stimulation of bacterial sulfur cycling activity in tuberospheres suggests that this microbial function may serve specific biological roles for potato tubers.