FIG. 2.

Growth of MIT 9215 in liquid Pro99 medium with or without helper heterotrophs. Dilutions of MIT 9215 were grown in the absence (A) or presence (B) of ∼5 × 10⁵ CFU of EZ55 ml⁻¹. Initial concentrations of MIT 9215 cells were 3.5 × 10⁰ (⧫), 3.5 × 10¹ (□), 3.5 × 10² (▪), 3.5 × 10³ (▵), 3.5 × 10⁴ (▴), 3.5 × 10⁵ (○), and 3.5 × 10⁶ (•) cells ml⁻¹. Error bars indicate one standard deviation of the mean for three replicate cultures. The dotted horizontal lines represent the limit of detection for chlorophyll-based fluorescence (10 arbitrary units [AU]); values below this limit were reported as 10 AU.