Bacteria were made to generate electricity when they encounter hazardous substances—and they did so by “trapping” them in a cell.

New biosensor system: bacteria as “electrical” detectors

Scientists have created a promising bio‑electronic sensor in which living bacteria generate an electrical signal upon detecting specific substances in liquid. The technology is based on a chitosan hydrogel—a natural polymer primarily derived from crustacean shells (but also from mollusks, fungi, insects). Because of this material, the sensor becomes safe even for food product monitoring; initial tests were conducted on milk, where it detects unwanted impurities.

How bacteria‑generators work
Bacteria capable of producing electricity have been known for a long time. Their diversity allows selecting suitable strains depending on which substances need to be detected. The problem was that when colonies are immersed in liquid they either wash out themselves or the mediator substance required to transfer electrons to electrodes is washed away.

Solution: chitosan hydrogel
The chitosan hydrogel acts as a “fortress”:

- it holds bacteria and mediators inside the medium;
- it provides a base for attaching redox mediators that transfer electrons from activated bacteria to electrodes.

Chitosan is safe for humans and the environment, and easily replaces synthetic carriers.

Sensor in action
When contacting target contaminants (e.g., toxic substances in wastewater or food products), microorganisms trigger an electron‑transfer respiratory chain. This produces a stable electrical signal that can be recorded with special equipment.

In a test run, a sensor with modified probiotic bacteria *Lactobacillus plantarum* was placed in milk. The bacteria respond to the presence of the preservative sakacin P, generating an electrical signal after several hours. Thus, the sensor successfully detected the target substance and exhibited electrical activity.

Prospects for application
The developed technology opens new possibilities for monitoring water quality and food products. In the future it can be implemented in industry, environmental control, and healthcare, contributing to a shift toward “green” solutions based on living microorganisms.