Chen, A.Y. et al. Nat. Mater. doi:10.1038/nmat3912 (23 March 2014).

Escherichia coli produce an extracellular amyloid material called curli that is involved in biofilm formation. The secreted major curli subunit, CsgA, self-assembles to form fibrils with great mechanical strength. Chen et al. harnessed control over this system to produce potentially useful functional materials using synthetic biology techniques. They engineered CsgA to contain a histidine tag and put it under the control of an anhydrotetracycline or acyl-homoserine lactone inducer–responsive riboregulator such that curli fibrils would be produced only in the presence of the cognate inducer. By tuning the delivery of the cognate inducers, they were able to generate curli fibrils that could be labeled with gold nanoparticles or quantum dots via the histidine tag. Such systems could be used to produce 'smart' biomaterials such as an environmentally responsive biofilm-based electrical switch.