Fig. 3

Growth competition experiments between SeptxD-2 and a natural competitor using phosphite as the only phosphorus source. aS. elongatus transgenic strain (SeptxD-2) and a natural competitor (Comp 1) were grown in monocultures and mixed cultures using BG-11 medium supplement with 0.2 mM phosphate (Pi) or 1.8 mM phosphite (Phi) as phosphorus source. Cultures were photographed 8 days after the inoculation. Cell number (cells/mL) was determined for the monocultures of SeptxD-2 (b), and the natural competitor 1 (Comp 1) (c), and for the mixed cultures under Phi (d) and Pi (e) treatments. Values are the mean of three replicates ± SD. Bars with asterisks are significantly different from the control (Student’s t test, *P < 0.05, **P < 0.01, ***P < 0.0001)