a, Synthetic gene circuits that couple curli subunit secretion to
external inducer signals, when combined with synthetic cellular communication
circuits, allow for the production of materials whose structure and composition
changes autonomously with time. AHLSender+aTcReceiver/CsgA
secreted both CsgA and AHL. As AHL signal accumulated,
AHLReceiver/CsgAHis secreted increasing levels of
CsgAHis. b, Using the autonomous cellular
communication system, the length of CsgAHis blocks and the proportion
of CsgAHis increased with time (plot of the proportion of fibril
length labelled by NiNTA-AuNP, grey lines). This behaviour could be tuned by the
ratio of the seeding density of AHLSender+aTcReceiver/CsgA
cells to AHLReceiver/CsgAHis cells. When only
AHLSender+aTcReceiver/CsgA cells were present, the
resulting fibrils were almost uniformly unlabelled; when only
AHLReceiver/CsgAHis cells were present, no curli
fibrils were formed (Controls). Detailed histograms can be found in Supplementary Fig. 10.
Scale bars are 200nm.