Characterization of a rationally engineered nitric oxide, nitrate and nitrite biosensor linked to a hybrid bacterial-­mammalian promoter

Synthetic biology is principally concerned with the rational design and engineering of biological systems that serve useful applied purposes. Biosensors are of particular interest to the field since they serve a broad array of applications, such as medical devices, environmental sensors for the detection of contaminants, toxins or pathogens or in metabolic engineering, to monitor product formation. In this study, we describe the characterization of a family of four nitric oxide, nitrate and nitrite whole­cell biosensors that are based upon a hybrid bacterial­-mammalian promoter design. The hybrid­ design of the synthetic promoter has been engineered for the detection of these nitrogenous species across both bacterial (Escherichia coli) and mammalian systems (MCF­-7). As such, these biosensors may be useful across applications as diverse as cancer therapeutics and the agricultural monitoring of nitrates and nitrites in fertiliser­ treated soil. Qualitative and quantitative analysis of these biosensors in E. coli confirmed that all four biosensor designs (termed B­M_eCFP, B­M_mRFP, M­B_eCFP and M­B_mRFP) were able to quantitatively detect 5-­20 mM of potassium nitrate. In summary, these pilot data suggest that, with further characterisation, this family of biosensors will be able to assess nitrogenous species present within both bacterial (E. coli) and mammalian systems (MCF­7).