= Rhizosphere
The <rhizosphere> is the region around a <root (botany)> whose conditions and <microorganisms> are influenced by the living <plant>, including through <root exudates>. It is distinct from the <rhizoplane>, the root surface, and from the internal root compartment. In an experiment, the boundary is operational: a collection protocol determines which material is assigned to each sample.<Defining the core Arabidopsis thaliana root microbiome by Derek S. Lundberg and others>[Abstract; Methods, General strategy]{ref}
A2012 <Arabidopsis thaliana> study compared <bulk soil> controls with <rhizosphere> material washed from <root (botany)>[roots] into buffer/detergent and an internal-root fraction obtained after removing surface-associated material by sonication. <DNA sequencing> of the bacterial <16S ribosomal RNA gene> revealed compartment-associated communities strongly influenced by <soil> type. Parallel unplanted <soil> controls helped distinguish root association from the starting community.<Defining the core Arabidopsis thaliana root microbiome by Derek S. Lundberg and others>[Abstract; experimental design; Methods, General strategy]{ref}
An invented sequencing example illustrates a measurement limit. A bacterial group contributing10percent of reads in <bulk soil> and20percent in a <rhizosphere> sample has doubled its relative read share. That alone does not show that its absolute cell count doubled: the total community size, other groups and measurement biases can differ. Sampling location and the measured quantity must both be stated.
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