Figure 2. Conversion of timing and amplitude of chemical inducer signals into material structure and composition.

a, Inducible synthetic gene circuits couple curli subunit secretion to external chemical inducers. Engineered cells containing these circuits can translate induction pulse length into nanoscale structure and composition of block co-fibrils. b, We first used AHL to induce secretion of CsgA from AHL_Receiver/CsgA and then used aTc to induce secretion of CsgA_His from aTc_Receiver/CsgA_His. We tuned the relative block lengths and proportions of CsgA and CsgA_His (plot of the proportion of fibril length labelled by NiNTA-AuNP, solid grey line) by changing the relative lengths of AHL versus aTc induction times. Scale bars are 200nm. c, Synthetic genetic regulatory circuits that couple curli subunit secretion to external inducer signals can translate inducer concentration into nanoscale structure and composition of block cofibrils. d, Engineered cells AHL induced secretion of CsgA from AHL_Receiver/CsgA, while at the same time, aTc induced secretion of CsgA_His from aTc_Receiver/CsgA_His. We tuned the relative block lengths and proportions of CsgA and CsgA_His by changing the relative concentrations of AHL and aTc inducers applied simultaneously. The solid grey line indicates the proportion of fibril length labelled by NiNTA-AuNP with varying concentrations of aTc and constant 100nM AHL. Detailed histograms can be found in Supplementary Figure 6. Scale bars are 200nm.