Table 3.
Reporter genes and their applications in whole-cell biosensors (WCBs).
| Reporter Gene | Signal Type | Mechanism | Advantages | Disadvantages |
|---|---|---|---|---|
| Lux (Bacterial luciferase) | Bioluminescence | Emits blue-green light (490 nm) via oxidation of a long-chain aldehyde produced by luxCDE | No need for exogenous substrates | Heat-labile |
| Luc (Firefly luciferase) | Bioluminescence | Produces visible light using luciferin, ATP, oxygen, and magnesium ions | High sensitivity and signal stability | Requires external substrates |
| Aequorin | Bioluminescence | Emits blue light upon oxidation of coelenterazine in the presence of calcium ions | High sensitivity and signal stability | Requires external substrates |
| GFP (Green Fluorescent Protein) | Fluorescence | Fluoresces green upon exposure to specific wavelengths | Easy expression by a single gene | High background signal, slow maturation |
| RFP (Red Fluorescent Protein) | Fluorescence | Fluoresces red upon exposure to specific wavelengths | Allows multianalyte assays | Less brightness compared to GFP, more prone to photobleaching |
| CFP (Cyan Fluorescent Protein) | Fluorescence | Fluoresces cyan upon exposure to specific wavelengths | Allows multianalyte assays | Less brightness compared to GFP, spectral overlap with GFP, potential toxicity |
| YFP (Yellow Fluorescent Protein) | Fluorescence | Fluoresces yellow upon exposure to specific wavelengths | Allows multianalyte assays | Less brightness compared to GFP, sensitive to pH changes, prone to photobleaching |
| β-galactosidase (lacZ) | Colourimetric/Fluorescence | Cleaves X-gal to produce a coloured product; can also use luminescent/fluorescent substrates | Versatile applications | Requires exogenous substrates and cell lysis; endogenous β-gal activity can cause background noise |
| Ice Nucleation Proteins (INPs) | Physical/Visual | Promotes ice crystal formation at warmer temperatures | Suitable for cold environments | Complex detection process, not real-time |
| Microbial pigments | Colourimetric | Produces visible colour changes via secondary metabolite pathways | Easily observable in field applications | Dependent on substrate availability |