Bioluminescence enhancement through an added washing protocol enabling a greater sensitivity to carbofuran toxicity

Reconstructing promoter activity from Lux bioluminescent reporters

The bacterial Lux system is used as a gene expression reporter. It is fast, sensitive and non-destructive, enabling high frequency measurements. Originally developed for bacterial cells, it has also been adapted for eukaryotic cells, and can be used for whole cell biosensors, or in real time with live animals without the need for euthanasia. However, correct interpretation of bioluminescent data is limited: the bioluminescence is different from gene expression because of nonlinear molecular and enzyme dynamics of the Lux system. We have developed a computational approach that, for the first time, allows users of Lux assays to infer gene transcription levels from the light output. This approach is based upon a new mathematical model for Lux activity, that includes the actions of LuxAB, LuxEC and Fre, with improved mechanisms for all reactions, as well as synthesis and turn-over of Lux proteins. The model is calibrated with new experimental data for the LuxAB and Fre reactions from Photorhabdus luminescens—the source of modern Lux reporters—while literature data has been used for LuxEC. Importantly, the data show clear evidence for previously unreported product inhibition for the LuxAB reaction. Model simulations show that predicted bioluminescent profiles can be very different from changes in gene expression, with transient peaks of light output, very similar to light output seen in some experimental data sets. By incorporating the calibrated model into a Bayesian inference scheme, we can reverse engineer promoter activity from the bioluminescence. We show examples where a decrease in bioluminescence would be better interpreted as a switching off of the promoter, or where an increase in bioluminescence would be better interpreted as a longer period of gene expression. This approach could benefit all users of Lux technology.

Bioluminescent reporters are used in many areas of biology as fast, sensitive and non-destructive measures of gene expression. They have been developed for bacteria, adapted now for other kinds of organisms, and recently been used for whole cell biosensors, and for real-time live animal models for infection without the need for euthanasia. However, users of Lux technologies rely on the light output being similar to the gene expression they wish to measure. We show that this is not the case. Rather, there is a nonlinear relationship between the two: light output can be misleading and so limits the way that such data can be interpreted. We have developed a new computational method that, for the first time, allows users of Lux reporters to infer accurate gene transcription levels from bioluminescent data. We show examples where a small decrease in light would be better interpreted as promoter being switched off, or where an increase in light would be better interpreted as promoter activity for a longer time.

Chemically individual armoured bioreporter bacteria used for the in vivo sensing of ultra-trace toxic metal ions

A chemically engineered mesoporous silica armour is developed for simultaneously improving bioreporter bacterial vitality and shielding infectivity.

Measurement of Bacterial Bioluminescence Intensity and Spectrum: Current Physical Techniques and Principles

: Bioluminescence is light production by living organisms, which can be observed in numerous marine creatures and some terrestrial invertebrates. More specifically, bacterial bioluminescence is the "cold light" produced and emitted by bacterial cells, including both wild-type luminescent and genetically engineered bacteria. Because of the lively interplay of synthetic biology, microbiology, toxicology, and biophysics, different configurations of whole-cell biosensors based on bacterial bioluminescence have been designed and are widely used in different fields, such as ecotoxicology, food toxicity, and environmental pollution. This chapter first discusses the background of the bioluminescence phenomenon in terms of optical spectrum. Platforms for bacterial bioluminescence detection using various techniques are then introduced, such as a photomultiplier tube, charge-coupled device (CCD) camera, micro-electro-mechanical systems (MEMS), and complementary metal-oxide-semiconductor (CMOS) based integrated circuit. Furthermore, some typical biochemical methods to optimize the analytical performances of bacterial bioluminescent biosensors/assays are reviewed, followed by a presentation of author's recent work concerning the improved sensitivity of a bioluminescent assay for pesticides. Finally, bacterial bioluminescence as implemented in eukaryotic cells, bioluminescent imaging, and cancer cell therapies is discussed.

The influence of carbon sources on the expression of the recA gene and genotoxicity detection by an Acinetobacter bioreporter

Bacterial whole-cell bioreporters are practical and reliable analytical tools to assess the toxicity and bioavailability of environmental contaminants, yet evidence has shown that their performance could be affected by different carbon sources. This paper evaluated the influence of carbon sources on the recA gene (ACIAD1385) in a DNA damage-inducible recA::luxCDABE Acinetobacter bioreporter and optimized the induction conditions for its practical application in environmental monitoring. Different carbon sources, including LB, potassium acetate (MMA), sodium citrate (MMC), sodium pyruvate (MMP), and sodium succinate (MMS), significantly influenced (p < 0.05) the bioluminescence intensity of the genotoxicity bioreporter. A reverse transcription quantitative PCR (RT-qPCR) showed the different expression levels of the DNA damage-inducible gene recA (p < 0.05), suggesting that carbon sources influenced the DNA damage response in the Acinetobacter bioreporter at the transcriptional level. Additionally, proteomic analysis identified 122 proteins that were differentially expressed after exposure to mitomycin C in defined media and LB, and 5 of them were related to the DNA damage response, indicating the effects of carbon sources on the DNA damage response in Acinetobacter at the translational level. The repression effect caused by the rich medium, LB, was possibly related to the mechanism of carbon catabolite repression. Our results suggest that the practical application of Acinetobacter bioreporters to the genotoxicity assessment of polycyclic aromatic hydrocarbon (PAH)-contaminated soils could be significantly improved by using a standard medium of defined composition, as this could increase their sensitivity.

Influence of carbon-based nanomaterials on lux-bioreporter Escherichia coli

The cytotoxic effects of carbon-based nanomaterials are evaluated via the induction of luminescent genetically engineered Escherichia coli bacterial cells. Specifically, two engineered E. coli bacteria strains of DPD2794 and TV1061 were incubated with aqueous dispersion of three carbon allotropes (multi-wall carbon nanotubes (MWCNTs), graphene nanosheets and carbon black nanopowders) with different concentrations and the resulting bioluminescence was recorded at 30°C and 25°C, respectively. The corresponding optical density changes of bacterial cells in the presence of various carbon nanomaterials were recorded as well. Based on these results, E. coli DPD2794 bacterial induction responds to a greater degree than E. coli TV1061 bacteria when exposed to various carbon-based nanomaterials. Finally, the surface morphology of E. coli DPD2794 bacteria cells before and after carbon-based nanomaterials treatment was observed using a field emission scanning electron microscope (FESEM), from which morphological changes from the presence of carbon-based nanomaterials were observed and discussed.