Engineered bacteria detect gut inflammation in mice

A new strain of engineered bacteria can detect inflammation in the colon of mice even after more than 1,000 bacterial divisions, researchers report (Nat. Biotechnol. 2017, DOI: 10.1038/nbt.3879). Such a microbe could help doctors diagnose and monitor diseases such as inflammatory bowel disease. Pamela A. Silver and coworkers at Harvard University engineered nonpathogenic Escherichia coli to detect and respond to tetrathionate, a transient product of a reactive oxygen species released by intestinal cells during inflammation. The researchers inserted two genetic circuits into the bacterial genome. The first circuit produces the transcriptional factor Cro in response to tetrathionate, and Cro triggers a second “memory” circuit to produce the protein β-galactosidase. Even when tetrathionate is no longer around, the bacteria “remember” the exposure and continue to produce both proteins. The researchers monitored inflammation in mice treated with the microbes by measuring β-galactosidase in the animals’ feces. The bacteria produced β-galactosidase in mice