Spatial distribution of the Pepper Blight suppressive microbiome in the rhizosphere

Properties of plant rhizosphere are supposed to be dynamic and heterogenous, serving as different habitats selecting for or against microorganisms. Herein, we studied the spatial distribution of bacterial communities in the rhizosphere of pepper treated by a disease-suppressive or non-suppressive soil. The spatial variation (36%) of bacterial community in the rhizosphere was much greater than those (10%) explained by soils. Bacterial richness and evenness in the rhizosphere decreased from the upper taproot to the upper fibrous root and the lower taproot and to the lower fibrous root. Taxa such as subgroups of Acidobacteria, Nitrosospira and Nitrospira known as aerobic heterotroph or chemoautotroph were selectively enriched at the upper taproot. In vitro Bacillus antagonists against Phytophthora capsici were also preferentially colonized at the taproot. While genera frequently involved in anaerobic fermentation of organic materials (Clostridium), nitrogen fixation (Rhizobium, Azotobacter), assimilatory or dissimilatory denitrification (e.g. Hydrogenophaga, Magnetospirillum) were enriched in the lower taproot or fibrous root. In conclusion, the spatial distribution of bacterial taxa and antagonists in the rhizosphere of pepper shed light into our understanding of microbial ecology in the rhizosphere.