Stable isotope probing of microbial nucleic acids applied in the rhizosphere enables (a) the identification of the active microbial community involved in root exudate assimilation and those involved in soil organic matter degradation, and (b) the study of the impact of plants via root exudates on the in situ expression of microbial functions. By incubating plants under 13CO2, fresh carbon exuded by the plant will be labeled and hence the microbial community assimilating 13C-root exudates will incorporate 13C into their cellular macromolecules. Labeled DNA, RNA, and proteins can be used to identify microorganisms that assimilated the root exudates. We provide a step-by-step protocol on how to apply stable isotope probing of DNA and RNA in the plant rhizosphere to identify the active microbial communities and analyze their gene expression.
Keywords: 13CO2 plant labeling; 16S rRNA; 18S rRNA; CsCl equilibrium density-gradient centrifugation; DNA; Isotope; RNA; Ratio mass spectrometry; Root exudates; Root system; Root-adhering soil; Stable isotope probing.