Patterning cells in multi-colored lines. a, For two overlapping radial gradients, the set of all points equidistant from the center of the two gradients is the location where the ratio of the concentration of the two compounds is a constant. b, Schematic of plasmid pBAD-Fluor, the third compatible plasmid harbouring the genes encoding either RFPec, eYFP or eCFP under the arabinose-inducible pBAD promoter. c, RH37 cells (harbouring pDIM-C8-P99bla, pTS1 and pBAD-Fluor-RFPec) were spread evenly on plates containing 30 μg/ml Tet. Discs containing Amp, IPTG, Tet and/or arabinose were placed at the indicated positions. Plates were incubated at 37°C. Visible light and merged fluorescent images are shown. The detailed conditions for all plates can be found in Additional file 1.