One of the problems with microplastics pollution lies in the fact that the plastic particles can be so small, we don't even know they're present in water in the first place. A new type of engineered bacteria could help, by causing those microparticles to glow green.
By definition, microplastics are fragments of plastic smaller than 5 millimeters in diameter.
Found in waterways around the world, they come from a number of sources. These include chunks of floating plastic waste that break down into smaller pieces; products such as toothpaste which contain plastic microbeads; synthetic clothing that sheds fibers while being washed; and car tires that release bits of rubber which make their way into storm sewers.
Researchers are still trying to understand how people's health may be affected by ingesting the particles in and of themselves. That said, harmful bacteria are often drawn to microplastics, living on or around the particles – and we definitely shouldn't be eating or drinking those microbes.
There are already methods of detecting microscopic plastic particles in water – methods such as Raman or infrared spectroscopy – but they are fairly time-consuming and labor-intensive. In other words, they're not practical to perform on a widespread, ongoing basis. That's where the altered Pseudomonas aeruginosa bacteria come in.
Prof. Song Lin Chua and colleagues from Hong Kong Polytechnic University added two genes to a non-infectious strain of the microbe. One of these genes produces a protein that becomes active when the bacteria come into contact with plastic, while the other gene produces another protein which fluoresces green in response to the first one.
It does so within three hours, and works on a number of different plastics. And what's more, the bacteria remain viable for up to three days if stored at a temperature of 39 ºF (4 ºC).
When tested on filtered seawater samples from a city's sewer system, the engineered bacteria were able to detect the presence of microplastic types such as polyacrylamide, polycaprolactone and methyl cellulose.
"Our biosensor offers a fast, affordable and sensitive way to detect microplastics in environmental samples within hours," says Chua. "By acting as a rapid screening tool, it could transform large-scale monitoring efforts and help pinpoint pollution hotspots for more detailed analysis."
A paper on the research was recently published in the journal ACS Sensors.
Source: American Chemical Society
