How glowing bacteria in the dirt can save lives

Researchers at the Hebrew University of Jerusalem have spent a decade developing living land mine sensors using E. coli bacteria. By using genetic engineering, they can turn each bacterium into “a miniature firefly” in the presence of a chemical associated with the explosives, said Shimshon Belkin, the Hebrew University microbiologist leading the research.

In 2019, more than 5,500 people were killed or injured by land mines and explosive remnants of war, and 80 percent of them were civilians, according to the International Campaign to Ban Landmines. Anti-personnel land mines, which can be only a few inches across and easily concealed, are especially dangerous. Estimates vary for the worldwide count of buried land mines, but they are as high as 110 million. Many strategies have been tried to locate land mines, such as using metal detectors and training detection animals, including an award-winning rat that helped locate 71 land mines before it retired. Each method balances benefits with risks and costs.

The idea of rewiring bacteria to sense land mines originated with Robert Burlage, then at Oak Ridge National Laboratory in Tennessee. In the mid-1990s, Dr. Burlage worked on getting bacteria to light up in response to organic waste and mercury. Looking for a new application for this technique, he got the idea to try targeting land mine chemicals.

Although Dr. Burlage conducted a few small field tests, he was unable to secure more funding and moved on. “My tale of woe,” said Dr. Burlage, now a professor at Concordia University Wisconsin. Dr. Burlage’s work was an inspiration for the Israeli researchers, and he says he wishes them well in their efforts to advance the technology. Bacteria are cheap and expendable and can be spread over a lot of ground. And they are relatively quick at reporting back — within hours, or up to a day, they either glow or they don’t.

Dr. Belkin and his team describe tinkering with two key components of the E. coli genetic code: pieces of DNA called “promoters” that act as on/off switches for genes, and “reporters” that prompt light-emitting reactions. To produce this effect, researchers borrowed genes from marine bacteria that naturally emit light in the ocean. These latest crops of genetically engineered bacteria are faster to react and more sensitive than bacteria in the group’s earlier field tests, Dr. Belkin said. And the scientists no longer need to use a laser signal to activate the glow. One key challenge the group is working to overcome is safely locating the bioluminescent bacteria in a real minefield. When they detect land mines, their glow is so faint that light from the moon, stars or nearby cities could drown it out.

To help address this problem, Aharon J. Agranat, a bioengineer at Hebrew University, and other researchers reported in April in the journal Biosensors and Bioelectronics that they had developed a device that shields the bacteria and detects their glow. This sensor system can then report its findings to a nearby computer, but it hasn’t been tested outside a laboratory setting. In the future, the team hopes to use drones to deploy bacteria sensors in a minefield, eliminating the need for humans to get close.

Landau is a journalist with NYT©2021

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