Fig. 4. Insulation of genetic circuits operating in parallel liposome populations.

a. Schematic of liposome populations designed to contain similar genetic components but to respond differently to the same environmental concentration of the non-membrane-permeable small molecule activator doxycycline (Dox), by expressing different amounts of the alpha-hemolysin channel protein (aHL). These liposomes contain a measured amount of the plasmid for constitutively expressed aHL, and of a plasmid driving either firefly luciferase (fLuc) or Renilla luciferase (rLuc) from the Tet inducible promoter (the luciferase plasmids were always held at the same concentration). Throughout this figure, the two populations were incubated together in the solution containing Dox and harvested after 6 h (see Figs. S11 and S12 for rLuc and fLuc expression as a function of aHL plasmid concentration, after 2 h and 6 h, respectively). b. Each liposome contains either 0.1 nM or 5 nM of the aHL plasmid. c. Luciferase expression in symmetrical populations, where the amount of aHL DNA is the same across the two populations; the amount of fLuc and rLuc expression is graphed with respect to aHL plasmid concentration and to each other. d–e. Luciferase expression in asymmetrical populations. d. Luciferase expression when Renilla liposomes have a constant aHL plasmid concentration (0.1 nM) but the concentration of that plasmid is varied in the firefly liposomes. Expression of rLuc and fLuc are graphed against the plasmid concentration in firefly liposomes and against each other. e. Luciferase expression as in d, but with constant aHL plasmid concentration in firefly liposomes and variable concentration in Renilla liposomes. Error bars indicate S. E. M. n=4 replicates.