Researchers have developed genetically engineered bacteria that can detect chemicals. A researcher involved says that the bacteria can monitor chemicals in laboratory experiments or unwanted chemicals in the environment.
The world increasingly needs to detect chemicals in various settings, including the bioproduction of industrial chemicals, in research or in monitoring chemicals in the environment – and how rapidly they accumulate or dissipate.
There are many ways to detect chemicals in various settings, but this is often costly and difficult. However, this may change now that researchers have designed bacteria that fluoresce when specific chemicals are present. If bacteria added to a water sample fluoresce green, the target chemical is present.
“Our method detects chemicals in various settings simply and inexpensively. We will use the method in our research and will make the method available to others detecting various chemicals in fields such as industrial production and environmental monitoring,” explains a researcher behind the method, Daniel C. Volke, Senior Researcher at the Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kongens Lyngby.
The research, which was carried out in collaboration with Javier M. Hernández-Sancho and Pablo I. Nikel, has been published in Nature Communications.
Making growth dependent on various chemicals
The researchers engineered a non-pathogenic soil bacterium, Pseudomonas putida, with the aim of turning it into a biosensor to detect various chemicals such as bacterially produced lactic acid, chemicals in the environment or breakdown products from the enzymatic degradation of polyethylene terephthalate (PET).
The researchers made the growth of the bacteria dependent on the target chemicals, eliminating the possibility of growing by using other carbon substrates.
Since the bacteria can only grow if the target chemicals are present, the growth of the bacteria shows whether the chemicals are present.
The researchers also equipped the bacteria with a gene for a fluorescent protein so that they light up. The more bacteria present, the more they light up overall, and the fluorescence shows the quantity of bacteria – whether their numbers are increasing and the rate at which this happens.
“The more of the target chemical present, the greater the density of the bacteria and the stronger the fluorescence. We can put the bacteria into a test tube containing an environmental sample or a sample from our laboratory and rapidly determine whether the target chemicals are present and whether one sample has more than another,” says Daniel C. Volke.
Fluorescence measured by mobile phone
Equipping the bacteria with a fluorescent protein enables the fluorescence and thereby the bacterial growth to be measured using technology available on a mobile phone. Target chemicals can thus be detected at any site.
Further, researchers can very easily change the bacteria’s genetic makeup so that they detect different target chemicals.
“If the target chemical is present, the bacteria begin to grow and glow, but if it is not present, nothing happens. In addition, Pseudomonas putida, unlike other bacteria, is very robust and can be used in many demanding conditions,” notes Daniel C. Volke.
Monitoring PET degradation
The researchers tested the bacteria’s ability to measure various chemicals as a proof of concept, showing that the bacteria in a tunable biosensor can detect lactic acid produced by other bacteria in biological experiments.
The researchers have also shown that the bacteria can measure the enzymatic degradation of PET. The bacteria were enabled to grow on the breakdown products and could thus show how effective the PET-degrading enzymes are and how rapidly the PET is degraded.
Daniel C. Volke says that the researchers do not want to launch a company based on their invention but hope that others will use these bacteria, just as they do in their own research.
“In our laboratory, the bacteria can rapidly show us whether other bacteria are producing the target chemicals. We add the fluorescent bacteria into the other bacteria, and if they light up, then the target chemical is present. The brightness also shows whether one strain of bacteria produces more of the chemical than another. Thus, this method can replace the expensive and slow analysis processes we use today,” he concludes.
