AsianScientist (Jun. 22, 2017) – Researchers from the Hiroshima University have developed a phosphite-based biocontainment strategy that makes using genetically-modified organisms (GMOs) safer. Their results have been published in Scientific Reports.
The use of GMOs—microorganisms not found in the natural world but developed in labs for their beneficial characteristics—is a contentious issue. While GMOs could greatly improve society in numerous ways—such as breaking down pollutants or increasing food production—many continue to fear what might happen should they escape into the environment.
Existing biocontainment strategies—methods to prevent GMO escape or proliferation beyond their intended use—typically employ one of two forms. One is the ‘suicide switch’ method, where released GMOs die off independently after a given time. The other is ‘nutrient requirement,’ where GMOs are designed to expire on removal of a nutrient source.
In the present study, Professors Ryuichi Hirota and Akio Kuroda made use of the fact that all living things require phosphorus for a vast array of life-determining processes including energy storage, DNA production and cell signal-transduction.
The overwhelming majority of bacteria use phosphorous from the naturally occurring nutrient, phosphate. However, bacteria are renowned for their ability to obtain energy from seemingly implausible sources and the researchers found one type, Ralstonia sp. Strain 4506, capable of utilizing non-naturally occurring phosphite instead. Phosphite, a waste by-product from the metal plating industry, does not occur in the natural world. Therefore, scientists can easily control its availability.
The researchers isolated strain 4506’s phosphite-digesting enzyme and introduced it into Escherichia coli bacteria. They also created a phosphite specific transporter to allow E. coli to take up phosphite. In addition, the team used gene editing to shut down the existing phosphate transporters present in E. coli.
When the resulting GMO was tested the results were outstanding. It proliferated in a phosphite medium, and didn’t grow at all when exposed only to phosphate. When thriving bacteria were later deprived of phosphite over two weeks, they completely died out.
Requiring just nine simple gene edits and using a readily available industrial waste product, this method of making GMOs is cost and time effective, the authors say. Additionally, its simplicity means it can be adapted for other microorganisms, making it highly versatile. These traits contrast with previous biocontainment strategies involving synthetic organisms and energy sources, requiring hundreds of gene edits, lots of money and time.
The authors hope that this new strategy will help to convince the public and government agencies that GMOs can be used safely outside of the lab and for the betterment of society.
The article can be found at: Hirota et al. (2017) A Novel Biocontainment Strategy Makes Bacterial Growth and Survival Dependent on Phosphite.
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Source: Hiroshima University; Photo: Ryuichi Hirota.
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