Fig. 4

Density sensing in populations of cell-mimics. a Artificial quorum sensing cell-mimics contain T3 activation cascade DNA templates and 240 × tetO plasmids. b Micrographs of cell-mimics in 4.5 µl droplets of TX-TL (left). The number of cell-mimics is indicated. Enlarged regions (indicated by white boxes) show presence and absence of fluorescence (green) in hydrogel nuclei after 3 h of expression. c Scatter dot plot of fluorescence intensities in individual cell-mimics at different densities. Each density category combines data in increments of 50 cell-mimics per droplet and contains data from at least 156 cell-mimics (Methods). Black bars show average fluorescence. d A 2-color response to density is achieved by adding a constitutively expressed reporter (pT7-tetR-mCherry), which is on independent of density. e 2-color density sensors were spread at increasing density in an elongated chamber (brightfield image, bottom). Panels above show magnified fluorescence images of indicated regions (mCherry fluorescence: magenta, left; sfGFP fluorescence: green, middle; merge of fluorescence channels: right). Images in each channel are window leveled to the same values and have a width of 70 µm. f Ratio between sfGFP to mCherry fluorescence in individual hydrogel nuclei along the chamber. Positions correspond to tile regions of the image above