Construction and Application of a Multicolor Bactosensor for Detecting Bioavailable Antibiotic Mixtures in the Environment

The advancement of synthetic biology has enabled transformative approaches for environmental monitoring, yet the simultaneous quantification of multiple co-occurring pollutants, an inherent feature of real environmental contamination, remains a significant challenge. In this study, we engineered a multicolor bactosensor capable of concurrently detecting tetracycline and erythromycin by integrating two transcription-factor-based sensing modules into a single plasmid and enhancing the performance by introducing antibiotic resistance genes. The bactosensor exhibited a high detection specificity toward individual tetracyclines and macrolides. Notably, it enabled quantitative discrimination of binary antibiotic mixtures through simple visual comparison of fluorescence color differences in bacterial images captured with a smartphone. The platform further demonstrated reliable accuracy in detecting antibiotics in real water samples. Overall, this work establishes a novel, field-deployable bactosensor for on-site quantification of antibiotic mixtures, particularly their bioavailable fractions, which are often overlooked in conventional chemical analyses.