FGE‐sulfatase‐based bacterial biosensor with single copy evolved sensing cassette for arsenic detection

BACKGROUND: Arsenic (As) is classified as a Group 1 human carcinogen, and the maximum arsenic contamination level allowed in drinking water is10 μg L⁻¹. In this study, a genetic‐based whole‐cell biosensor for arsenic detection was constructed and engineered for rapid and more efficient arsenic detection. RESULTS: The promoter and repressor responsive to arsenic (ArsBR) were newly isolated from Bacillus cereus ATCC14579. The reporter gene was atsBA carrying formylglycine‐generating enzyme (FGE) and sulfatase, which provided a fluorescent product after reacting with 4‐methylumbelliferyl sulfate (4‐MUS). To improve the performance of the arsenic biosensor, firstly, more efficient Escherichia coli host strains were constructed, including the disruption of the arsenic efflux pump, multidrug efflux pump and arsenical‐resistant genes; secondly, a repressor (ArsBR) was engineered by an error‐prone polymerase chain reaction (PCR) technique, aiming to lower the detection limit; lastly, a single copy biosensor cassette in an E. coli chromosome was constructed. CONCLUSION: The stable and sensitive biosensor was able to detect As(III) at 5 μg L⁻¹ and As(V) at 50 μg L⁻¹ in 3.5 h with a very low fluorescent background. Moreover, the roles of all seven cysteine residues of the repressor were also investigated. Interestingly, the six cysteine residues Cys 28, 34, 36, 89, 90 and 100 are functionally involved in arsenic sensing, but not Cys 101. © 2019 Society of Chemical Industry