Fig. 3

Fluorescence-based detection of the AGTR1 signaling stimulated by the secreted Ang II peptide using engineered yeast in droplet cultures. A Single colonies were picked up and cultured in SD medium in test tubes. W/O droplets were generated to encapsulate single yeast cells in SDM71 medium, as shown in Fig. 2A, and then statically incubated at 30 °C. The yeast cells in droplets were observed under a fluorescence microscope, and the gray values were measured by machine-learning-based image processing, as shown in Fig. 2B. B Bright-field images of droplets incorporating Ang II-secreting yeast cells (AGII), and the percentage of droplets incorporating the different yeast cell counts (excluding empty droplets). C Fluorescence images of yeast-incorporated droplets in droplet cultures at 9 h of cultivation. D Time course of the GFP gray values of the yeast cells contained in the P2′ region (Additional file 1: Fig. S4B; fluorescent population) under droplet-culture conditions. The gray values of > 100 samples of yeast-incorporated droplets were calculated. The error bars represent the mean (± SD) of more than 100 samples. N.D. = not detected