Fig. 3.

Engineering polymicrobial communities. (A) Staphylococcus aureus and P. aeruginosa cells are embedded in one precursor gel to form a physically mixed polymicrobial community. Bright-field images acquired at 37 °C over 10 h show growth of the mixed colony, with the enclosure (initially 8 pL) roof and walls distending dramatically over the last several hours of growth (Movie S2). Eventually, the structure’s 2-μm-thick roof ruptured, releasing cells into the surrounding medium (not shown). S. aureus and P. aeruginosa cells are false-colored red and green, respectively, for visualization in the “0 min” and “80 min” images. (B) Cut-away 3D mask reconstructions (Upper) and bright-field images (Lower) depict examples of nested polymicrobial communities of varying geometries and cell densities (see also Fig. S3). Low-density (Left) and high-density (Right) S. aureus microclusters are confined in rectangular and hemispherical cavities, respectively, surrounded by high-density P. aeruginosa populations. Inner cavities are 1 pL and outer chambers are 30 pL. The 5-μm-thick roofs used to seal in inner cavities and the outer chambers are not visible in the bright-field images. (Scale bars, 10 μm.)