One day, you might be able to diagnose a gut disease by the color of your poop. Researchers have developed bacteria that produce a pigment when certain molecules associated with colon inflammation are detected, which then pass out with your feces.
The work builds on previous research that was first conducted back in 2009. Scientists at Cambridge University genetically engineered Escherichia coli bacteria to detect certain molecules and then secrete particular pigments that are visible to the naked eye. The pigment genes were taken from existing organisms and could produce a range of colors, from red to yellow to violet.
In theory, this could mean that the modified bacteria could also be used to detect toxins in water, for example, and then produce a pigment in response, even allowing people to see what the concentration of that toxin might be. Their issue when it came to the gut, however, was how long the bacteria would be able to survive, limiting its use as a diagnostic tool.
This latest research, published in Nature Biotechnology, seems to have found a way around that. They created modified E. coli that can survive for up to six months inside the gut of mice, greatly increasing its potential use in medicine. The team designed the E. coli so that it can sense a substance known as tetrathionate. This chemical is elevated in patients who have ulcerative colitis, a long-term condition in which the colon and rectum are inflamed.
They then took healthy mice, as well as mice that had inflammation similar to ulcerative colitis, and populated them with the engineered E. coli. When the bacteria finds tetrathionate, it turns on a pathway that leads to the production of a blue pigment. The researchers then took the poop from the mice, isolated the bacteria, and grew them. In those mice with inflammation, the normally white bacteria were now colored blue.
This experiment was simply a proof of concept that the technique works and can be modified. There are obviously limitations if it were to be used as a diagnostic tool, mainly that it still requires someone in the lab to isolate and culture the bacteria from a patient's feces.
However, this might not always need to be the case. The gene that codes for the blue pigment, for example, could be swapped for one that produces fluorescent proteins, meaning that the patient would be able to see for themselves if there are any issues. They could even produce a range of different bacteria that detect various molecules and produce different colored pigments.
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