Genetically Engineered Bacteria Enable Self-Powered Biosensors
Recent advances in synthetic biology and bioelectrochemistry have led to the development of self-powered chemical sensors using genetically engineered bacteria. Researchers from Imperial College London and Zhejiang University have created living biosensors that convert chemical signals into electrical outputs. These devices promise low-cost, portable, and programmable bioelectronic applications.
Limitations of Traditional Biosensors
Conventional biosensors often rely on enzymes. They tend to be fragile and expensive. Their response times can be slow, especially in complex environments. Optical signals from whole-cell biosensors are difficult to integrate with portable electronics. These issues limit their practical use in field conditions.
Engineering Bacteria for Electrical Signal Output
Researchers used Escherichia coli bacteria as biological platforms. The bacteria were genetically modified to include three modules – sensing, information processing, and output. The sensing module detects target chemicals using molecular regulators. The processing module amplifies or modifies the signal. The output module produces phenazines, nitrogen-containing molecules detectable by electrochemical techniques.
Detection of Specific Chemicals
Two biosensors were developed. The first detected arabinose, a plant sugar. Upon sensing arabinose, bacteria produced phenazine-1-carboxylic acid, generating an electrical current proportional to sugar concentration within two hours. The second biosensor targeted mercury ions in water. A genetic amplifier enhanced phenazine production when mercury bound to the MerR protein. This allowed detection of mercury at 25 nanomoles, below World Health Organization safety limits, within three hours.
Logical Operations Within Living Sensors
The team also engineered an ‘AND’ logic gate inside E. coli. This gate triggered a signal only when two specific molecules were present simultaneously. This demonstrates the potential for complex biochemical computing within living biosensors.
Applications and Advantages
These living biosensors can self-maintain and operate in contaminated environments. Their electrical outputs are compatible with low-cost electronics, enabling portable devices. This approach could revolutionise environmental monitoring, medical diagnostics, and food safety testing.
About Escherichia coli
E. coli is a common bacterium in the intestines of humans and warm-blooded animals. Most strains are harmless. Some, like Shiga toxin-producing E. coli (STEC), cause severe foodborne illnesses. STEC transmits mainly through contaminated foods such as undercooked meat, raw milk, and raw vegetables. It produces Shiga toxins similar to those from Shigella dysenteriae. STEC grows between 7 °C and 50 °C, optimally at 37 °C. It can survive in acidic foods (pH 4.4) and requires a minimum water activity of 0.95. Cooking food to 70 °C or higher destroys STEC. E. coli O157:H7 is the most STEC strain for public health, but others also cause outbreaks.
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