Analysis of bioavailable toluene by using recombinant luminescent bacterial biosensors with different promoters

Abstract

In this study, we constructed recombinant luminescent Escherichia coli with T7, T3, and SP6 promoters inserted between tol and lux genes as toluene biosensors and evaluated their sensitivity, selectivity, and specificity for measuring bioavailable toluene in groundwater and river water. The luminescence intensity of each biosensor depended on temperature, incubation time, ionic strength, and concentrations of toluene and coexisting organic compounds. Toluene induced the highest luminescence intensity in recombinant lux-expressing E. coli with the T7 promoter [T7-lux-E. coli, limit of detection (LOD) = 0.05 μM], followed by that in E. coli with the T3 promoter (T3-lux-E. coli, LOD = 0.2 μM) and SP6 promoter (SP6-lux-E. coli, LOD = 0.5 μM). Luminescence may have been synergistically or antagonistically affected by coexisting organic compounds other than toluene; nevertheless, low concentrations of benzoate and toluene analogs had no such effect. In reproducibility experiments, the biosensors had low relative standard deviation (4.3–5.8%). SP6-lux-E. coli demonstrated high adaptability to environmental interference. T7-lux-E. coli biosensor—with low LOD, wide measurement range (0.05–500 μM), and acceptable deviation (− 14.3 to 9.1%)—is an efficient toluene biosensor. This is the first study evaluating recombinant lux E. coli with different promoters for their potential application in toluene measurement in actual water bodies.

Recovery and genetic characterization of black queen cell virus

“…In our study, the bee mortality was about 60 % at days 7 after infection with synthetic BQCV RNA (1012 copies), while the mortality (about 30 % after 7 days) of inoculating adult honeybees with wild BQCV RNA (108 copies) with injection was relatively low [17], suggesting that BQCV virulence in this study was high. The reduced infection efficiency could be explained by the use of SP6 promoter to in vitro transcribe the viral RNA in Benjeddou et al study [42], while the PCR product containing the T7 promoter and a full-length copy of the BQCV genome was used as a template in the in vitro transcription reactions in our study, due to T7 promoter exhibited competitive advantages over previously reported biosystems than SP6 promoter [43]. In our previous study, we also constructed an infectious clone for IAPV and CBPV using the same method [21].…”

Highly Sensitive Luminescent Bioassay Using Recombinant Escherichia coli Biosensor for Rapid Detection of Low Cr(VI) Concentration in Environmental Water

“…However, it was inefficient in indicating the level of genotoxicity of Cr(VI) at low concentrations [36]. The satisfactory LOD of our sensors relative to previous sensors was due to the high activity of the chrB gene from O. anthropi YC211 and the position-appropriate promoters placed before the reporter gene lux [9].…”

“…However, it was inefficient in indicating the level of genotoxicity of Cr(VI) at low concentrations [36]. The satisfactory LOD of our sensors relative to previous sensors was due to the high activity of the chrB gene from O. anthropi YC211 and the position-appropriate promoters placed before the reporter gene lux [9]. Consequently, by virtue of the aforementioned reliable calibration curves for the Cr(VI) concentration range of 0.075-0.5 mg/L for the all biosensors or the Cr(VI) concentration range of 0.0005-0.75 mg/L (for T7-lux-E. coli biosensor), 0.001-0.75 mg/L (for T3lux-E. coli biosensor), and 0.005-0.75 mg/L (for SP6-lux-E. coli biosensor), the Cr(VI) concentration in the water samples could be accurately and rapidly determined.…”

“…R 2 values for these equations were quite high (>0.999), representing their high reliability. The concentration-dependent differences in these linear relationships may be due to differences in promoter characteristics [9,40]. In addition, the LOD values of Cr(VI) measurement by the T7-lux-E. coli, T3-lux-E. coli, and SP6-lux-E. coli biosensors were calculated as 0.0005, 0.001, and 0.005 mg/L, respectively.…”

“…Additionally, they only measure total metals but cannot distinguish between bioavailable and biounavailable metal concentrations or analyze the toxicity of metals [7,8]. By contrast, biological methods are useful alternatives because they can detect bioavailability and are low cost, easy to use, small, portable, highly sensitive, and highly selective [5,9]. Of the biological methods, bacterial biosensors are suitable for application as environmental sensors and early warning devices, even for on-field measurements [10].…”