Fig. 4.

Chemotactic response of B510 towards rice root exudates.

The chemotactic response of B510 was analyzed using a negative control (water), positive control (100 mM Malic acid), and root exudates from rice roots. Rice seedlings were grown in RG media including control, 1 mM KNO₃, 1 mM NH₄Cl, or 1 mM NH₄Cl+100 mM MES for 10 d without an inoculation or an inoculation with B510. Before transplantation, seedlings were washed twice in sterilized distilled water and transplanted to 30 mL sterilized distilled water for 2 d. A 50-fold concentrated root exudate (10 μL) was added to the center of each Petri dish (90 mm). The bacterial chemotactic response was triggered after an incubation at room temperature for 10 min. A response correlated with the appearance of a ring of turbidity near the center of each Petri dish. Scale bars=1 cm. The experiment was repeated three times with similar results.