Sensing the Right Time to Be Productive Francesca Ceroni, Benjamin A. Blount, Tom Ellis  Cell Systems  Volume 3, Issue 2, Pages 116-117 (August 2016) DOI: 10.1016/j.cels.2016.08.004 Copyright © 2016 Elsevier Inc. Terms and Conditions

Figure 1 A Two-Gate System Sensing Cell Density and Precursor Availability Reduces the Burden of Biosynthesis on E. coli A system that triggers an autonomous switch from growth to molecule production in engineered E. coli is described by Lo et al. This modular genetic system triggers expression of biosynthesis pathway enzymes in response to a growth-sensor that detects cell density and a substrate-sensor that detects precursor molecules. Unless both the conditions necessary for activation are present the system does not activate (a, b and c). Only when high cell density is reached and precursor is available the switch activates (d). Promoter PcsiD responds to cell density by sensing growth media nutrient quality. It activates expression of a coA-ligase enzyme (Fcs). Pathway precursors are converted into their CoA-forms by Fcs and bind to the PP3359 transcription factor inhibiting its repression of the promoter Pech. This promoter then activates expression of the downstream enzymes of the metabolic pathway that converts the CoA-form of the precursor into products. Cell Systems 2016 3, 116-117DOI: (10.1016/j.cels.2016.08.004) Copyright © 2016 Elsevier Inc. Terms and Conditions