Colonization Mechanism of Endophytic Enterobacter cloacae TMX-6 on Rice Seedlings Mediated by Organic Acids Exudated from Roots

Small molecular organic acids (SMOAs) in root exudates are critical for plant-microbe interaction, especially under environmental stresses. However, the dominant organic acids driving the process and promoting the colonization are unclear. Here, using a target metabolomics, 20 main SMOAs of rice root exudates were identified and analyzed in control and 10 mg/L thiamethoxam-treated groups. The composition of these SMOAs differed significantly between the two treatments. Among which, malic acid, citric acid, succinic acid, and proline induced a chemotactic response, swimming ability, and biofilm formation of Enterobacter cloacae TMX-6 in a dose-dependent manner. The maximal chemotactic response of TMX-6 was induced by proline at 10 mg/L, and a strong chemotactic response was even observed at 0.01 mg/L. The recruitment assay confirmed that the addition of these four compounds promoted the colonization of TMX-6. The results provide insight for directional regulation of plant-microbe interactions for beneficial outcomes.

Automated summary

Through targeted metabolomics analysis, 20 main small molecular organic acids (SMOAs) in rice root exudates were found to differ significantly between the control group and the 10 mg/L thiamethoxam-treated group. Among these, malic acid, citric acid, succinic acid, and proline were found to induce chemotactic response, swimming ability, and biofilm formation of Enterobacter cloacae TMX-6 in a dose-dependent manner. It was confirmed that the addition of these four compounds promoted the colonization of TMX-6. This study provides important insights for directional regulation of beneficial plant-microbe interactions.