Fig. 5

Detection of fluorescence among mixed yeast cells in batch and droplet cultures. Model yeast libraries were prepared using different mixing ratios of Ang II-secreting yeast cells (AGII) and non-secreting yeast cells (mock). A GFP gray values of the yeast cells contained in the P2′ region (Additional file 1: Fig. S4B) in droplet cultures. Single colonies of the AGII and mock strains were picked up and cultured separately in SD medium in test tubes. Using the mixed cell cultures with the indicated ratios, 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 for 9 h. The yeast cells in the droplets were observed under a fluorescence microscope, and the gray value was measured by machine-learning-based image processing, as shown in Fig. 2B. The gray values of > 100 samples of yeast-incorporating droplets were calculated, and the average gray values of yeast cells in the P2′ region were extracted. The error bars represent the mean ± SD of more than 100 samples. B GFP fluorescence intensities in the P2 region (Additional file 1: Fig. S4A) in batch cultures. Single colonies of the AGII and mock strains were picked up and cultured separately in SD medium in test tubes. The mixed cell cultures with the indicated ratios were inoculated into SDM71 medium in flasks, and then cultured at 30 °C, and shaken at 150 rpm for 9 h. Approximately 10,000 cells were analyzed by flow cytometry, and the average fluorescence intensities of yeast cells in the P2 region were calculated. The error bars represent the mean ± SD of three independent experiments. N.D. = not detected