approaches, which typically encapsulate bacteria in hydrogels, have produced deployable optical sensors for explosives14, heavy metals15 and chemical inducers16,17

current state-of-the-art whole-cell biosensors for field applications34,35, such as hydrogel-based20,36 and liquid-in-a-cartridge devices37

However, long-term live imaging is laborious and equipment intensive, because a single microscope often has to be monopolized for the duration of the experiment

. When E. coli metabolizes Collilert-18’s nutrient-indicator, MUG, the sample also fluoresces. It is reported that the method is able to detect a single viable coliform or E. coli per sample

In this paper, we designed a system that could fully repress lycopene production in the absence of an inducer and produce visible lycopene within two hours of induction. We engineered Lac, Ara, and T7 systems to be up to 10 times more repressible, but these improved systems could still not fully repress lycopene. Translational modifications proved much more effective in controlling lycopene. By decreasing the strength of the ribosomal binding sites on the crtEBI genes, we enabled full repression of lycopene

In the biosensor, the promoter regions of lasI, rhlI, pqsA, and ambB (QS genes) controlled the fluorescent reporter genes of Turbo YFP, mTag BFP2, mNEON Green, and E2-Orange

In this review, the most common traditional techniques, such as cyclic voltammetry, chronoamperometry, chronopotentiometry, impedance spectroscopy, and various field-effect transistor based methods are presented along with selected promising novel approaches, such as nanowire or magnetic nanoparticle-based biosensing

In situ probes using fluorescence and infrared spectroscopy are also available on the market and have been extensively studied

Biosensing intracellular concentrations of metabolites can provide an efficient high-throughput screen of hyperproducing strains.

bioluminescence was observed during the incubation time between 90 and 150 min in the presence of a sole carbon source such as glucose, acetate, l-glutamate and BOD standard solution (GGA solution)

We also show how our toolbox can be used to deploy the FBP in planta to build auto-luminescent reporters for the study of gene-expression and hormone fluxes

Because growth conditions (i.e., fluid dynamics and nutrient composition) can also have a profound effect on when QS is important,(71-75) there is a need to study biofilm formation and QS of BNR bacteria under various potential operating conditions.

difficult to observe in situ at the microscale, hence mechanisms and time scales relevant for bacterial spatial organization remain largely qualitative.

For in situ studies of AHL-dependent signaling in complex habitats, biosensors utilizing fluorescent proteins (GFP and RFP) as reporter genes have been developed

biosensors were employed to demonstrate AHL-mediated communication in swarm colonies of Serratia liquefaciens

it is unclear to what extent these results are relevant in natural habitats, as the standard assays neglect the different surface chemistries, interactions with other species, and physical constraints of natural environments.

This biosensor will help identify organic substrates that potentially support microbial growth and activity before and during nodulation

Such biosensors can reveal intriguing aspects of the environment and the physiology of the free-living soil S. meliloti before and during the establishment of nodulation, and they provide a nondestructive, spatially explicit method for examining rhizosphere soil chemical composition

quantifying biogeochemical fluxes resulting from these reactions remains a challenge

These tools provide insights into processes such as N uptake at the scale of individual root tips, allowing observation of plant–microbe interactions on scales at which they actually occur, instead of being masked by a whole‐core average

more convenient and effective methods is required for qualitative and quantitative analysis of AHLs

Now synthesized microbial biosensors are able to target specific toxins such as arsenic, cadmium, mercury, nitrogen, ammonium, nitrate, phosphorus and heavy metals, and respond in a variety of ways. They can be engineered to generate an electrochemical, thermal, acoustic or bioluminescent signal when encountering the designated pollutant.

Several bacterial strains have been engineered to detect transient gene expression in the laboratory8,9,10,11 and in vivo for up to 12 d12,13

microbial bioreporters (Table 2) report their perception of, or response to, their environments

For example, bacteria could be engineered to seek out hazardous chemicals or heavy metals in the environment, perform cleanup and return to their origin to report on the number of hazardous sites encountered via analysis by microfluidic devices