Rhizosphere soil architecture determined rhizospheric microbiome acquisition
Our results demonstrate that soil physical architecture surrounding the root zone was associated with the recruitment of rhizosphere microbiome from bulk soil, but only at the basal zone of the root system, possibly because the apical root has such a short soil-residence period (1 day vs 15 days of basal root) to change rhizosphere porosity. In addition, basal roots may accumulate more root exudates in the rhizosphere than at the root tip, which may modulate rhizosphere porosity (Rabbi et al., 2021). In the rhizosphere of basal root, increased soil porosity was correlated with enriched Actinobacteria, Acidobacteria, and Chloroflexi microbes, but reduced Firmicutes microbes and one core ASV, annotated as unclassified Micrococcaceae (Fig. 6 ). Modification of soil porosity by root elongation can alter microhabitats, through changes in gas and water flow (Young and Bengough, 2018). In chickpea plants, a more porous architecture of rhizosphere soil can favour water and gas permeability (Rabbi et al., 2018; Rabbi et al., 2021). Firmicute bacteria might prefer the rhizosphere microsite with smaller pore volume and less oxygen, as Firmicutes included the Clostridia class, which is a group of anaerobic bacteria (Teixeira et al., 2010). The enrichment and isolation under anaerobic conditions also confirmed a higher diversity of Firmicute isolates (Malele et al., 2018).