Plant conditioning of the rhizopshere bacteriome

We grew 19 herbaceous plant species from 5 plant orders in a common soil to test the effect of plant phylogeny on the conditioning of the rhizosphere bacterial flora. Total DNA from soils before and after conditioning was subjected to 16S rRNA gene high-throughput amplicon sequencing. Overall, 55% of the rhizosphere bacterial community was altered by plant conditioning. This change was largely independent of the taxonomic rank of plant species ranging from species, genus, family to plant order. Most prominent responders across all plant species were members of the little explored phyla Chloroflexi and Parcubacteria that sustained among the most abundant species-level populations after conditioning. Only a minor proportion of the rhizosphere bacteria responded either positively (ca. 1%) or negatively (ca. 1%) to conditioning in a plant-species specific manner. A substantial part of common and plant-specific positive responders could be attributed to rare biosphere bacteria, highlighting that such low-abundance populations are metabolically active in the rhizosphere.