title: Tunable reporter signal production in feedback-uncoupled arsenic bioreporters.
abstract: Escherichia coli-based bioreporters for arsenic detection are typically based on the natural feedback loop that controls ars operon transcription. Feedback loops are known to show a wide range linear response to the detriment of the overall amplification of the incoming signal. While being a favourable feature in controlling arsenic detoxification for the cell, a feedback loop is not necessarily the most optimal for obtaining highest sensitivity and response in a designed cellular reporter for arsenic detection. Here we systematically explore the effects of uncoupling the topology of arsenic sensing circuitry on the developed reporter signal as a function of arsenite concentration input. A model was developed to describe relative ArsR and GFP levels in feedback and uncoupled circuitry, which was used to explore new ArsR-based synthetic circuits. The expression of arsR was then placed under the control of a series of constitutive promoters, which differed in promoter strength, and which could be further modulated by TetR repression. Expression of the reporter gene was maintained under the ArsR-controlled Pars promoter. ArsR expression in the systems was measured by using ArsR-mCherry fusion proteins. We find that stronger constitutive ArsR production decreases arsenite-dependent EGFP output from Pars and vice versa. This leads to a tunable series of arsenite-dependent EGFP outputs in a variety of systematically characterized circuitries. The higher expression levels and sensitivities of the response curves in the uncoupled circuits may be useful for improving field-test assays using arsenic bioreporters.
authors: Department of Fundamental Microbiology, University of Lausanne, 1015 Lausanne, Switzerland.
authors: Davide
authors: D
authors: Merulla
authors: Vassily
authors: V
authors: Hatzimanikatis
authors: Jan Roelof
authors: JR
authors: van der Meer
mesh_terms: D001151:Arsenic / Q000032:analysis*; D015374:Biosensing Techniques / Q000379:methods*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D060847:Metabolic Engineering; D012680:Sensitivity and Specificity
chemical_list: D008164:Luminescent Proteins; D001151:Arsenic