Distinct root exudation patterns in emergent plants yield similar rhizosphere microbial communities

Distinct root exudate profiles are linked to root morphology in emergent plants. • We observed similar rhizosphere microbial communities despite distinct root exudate profiles. • Root exudates of Z. latifolia exert chemotactic attraction toward denitrifiers such as Pseudomonas and Acinetobacter . • Core metabolites, including phthalic acid and allantoin, can predict shifts in denitrification microorganisms. Emergent plants with different root morphologies show considerable variation in their nitrogen removal capabilities via nitrification and denitrification processes; however, the underlying mechanisms are still unknown. This study investigates how root morphology influences root exudates and rhizosphere microbial communities in two emergent plant species: Zizania latifolia (taprooted) and Pontederia cordata (fibrous-rooted). Root exudates were collected and analyzed using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), revealing distinct metabolic profiles between the two species. Z. latifolia primarily secreted benzenoids, while P. cordata exuded higher levels of lipids and lipid-like molecules. Despite these differences, the rhizosphere bacterial and fungal communities of both plants were similar in both structures and potential functions. Interestingly, the differential metabolites identified in Z. latifolia root exudates, especially amino acids (e.g., L-Valine and D-Proline), exhibited significant and positive correlations with denitrifying bacterial genera, such as Pseudomonas and Acinetobacter , suggesting that these metabolites exhibit strong chemotactic attraction toward specific microbial communities. Specifically, the chemotactic response of Pseudomonas sp. and Acinetobacter sp. to phthalic acid, allantoin, and quinic acid confirmed that these metabolites might recruit denitrifying microorganisms through chemotaxis. These findings highlight the complex interactions between root exudates, rhizosphere microbes, and nitrogen cycling in emergent plants, providing insights for optimizing wetland restoration strategies. Download: Download high-res image (351KB) Download: Download full-size image