(A, B) Photosynthetic activity and growth measurement (A) and fluorescence-activated cell sorting (FACS) analyses (B) of S. quadricauda MZCH 10104 in coculture with the strain Dyadobacter sp. HH091. (A) Increased photosynthetic activity and growth rate (optical density at 750 nm [OD 750 nm]) can be observed in the coculture with HH091. (B) Comparison of populations, based on chlorophyll intensity. Orange shading indicates a stable distribution of bacteria (population I), dead and lysed algae (population II), and healthy microalgae (population III) in the coculture at the end of the experiment (13 days). Blue shading shows how the proportion of dead and lysed algae is increased in the culture without HH091. The raw data are available in Fig. S2. (C) Images of cell sorting acquired with CLSM Axio Observer.Z1/7 LSM 800 (Carl Zeiss Microscopy GmbH, Jena, Germany) and ZEN software (version 2.3; Carl Zeiss Microscopy GmbH). Bar = 5 μm. Pulse-amplitude-modulation (PAM) fluorometry and FACS analyses demonstrated the improved fitness of S. quadricauda cocultured with HH091.