The ultimate goal is to be able to inject bacterial into the patient's body and then use ultrasound machines to hit the engineered bacteria with sound waves to generate images that reveal the locations of the microbes. The pictures would let doctors know if the treatments made it to the right place in the body and were working properly.

Mikhail Shapiro, assistant professor of chemical engineering said, "We are engineering the bacterial cells so they can bounce sound waves back to us and let us know their location the way to ship or submarine scatters sound when another ship is looking for it." The study results were published in the journal Nature

The idea of ??using bacteria as medicine is not new. Probiotics have been developed to treat the conditions of the gut, such as irritable bowel disease , and some early studies have shown that bacteria can be used to target and destroy cancer cells.

However, visualizing these bacterial cells as well as communicating with them, both to gather intel on what's happening in the body and give the bacteria instructions about what to do next. Imaging techniques that rely on light as taking pictures of cells tagged with a "reporter gene" that codes for green fluorescent protein only work in tissue samples removed from the body.

This is because light can not penetrate into deeper tissues like the gut, where the bacterial cells would reside. Shapiro wants to solve this problem with ultrasound techniques because sound waves can travel deeper into bodies.

The team's next goal was to transfer the genes for making gas vesicles from the water-dwelling bacteria into a different type of bacteria Escherichia coli , which is commonly used in microbial therapeutics, such as probiotics.

"We wanted to teach the  E.coli  bacteria to make the gas vesicles themselves," said Shapiro. "I have been wanting to do this ever since we realized the potential of gas vesicles, but we hit some roadblocks along the way, when we finally got the system to work, we were ecstatic."

One of the challenges the team hit involved the transfer of the genetic machinery for gas vesicles into  E.coli . They used gas-vesicle genes from a closer relative of  E.coli , a bacterium called Bacillus megaterium . Finally, the team tried to mix genes from both species and it worked.

The  E.coli  made gas vesicles on their own. Subsequent experiments from the team demonstrated that the engineered  E.coli  could indeed be imaged and located within the guts of mice using ultrasound.

"This is the first acoustic reporter gene for use in ultrasound imaging ," says Shapiro. "We hope it will ultimately be for ultrasound what green fluorescent protein have you done for light-based imaging techniques, what is it to really revolutionize the imaging of cells in ways there were not possible before."

The scientists say the technology should be available soon to those who research in animals, although it will take many more years to develop the method for use in humans.