In Grenoble, France, scientists have found a surprising new use for bacteria: predicting how sick someone with COVID-19 might get. The research team, working out of INRAE along with Grenoble Alpes University Hospital, Université Grenoble Alpes, and the CEA, discovered that a common gut bacterium called Escherichia coli—usually just called E. coli—can analyze blood samples and tell doctors which patients will likely recover at home and which might need hospital care. The findings were published in the journal Cell Systems.
What makes this approach unusual is that researchers didn't change the bacteria's DNA at all. They simply used what E. coli already knows how to do: detect signals in its environment and respond by adjusting how it grows. When placed in contact with COVID-19 patient plasma, the bacteria grew faster or slower depending on the chemical signals present. By measuring these growth patterns, scientists could sort patients into two groups—those heading toward mild symptoms and those at risk of severe disease.
Most surprisingly, a bacterium that had never been "trained" on medical data could perform classification tasks that normally require computer algorithms. "Rather than viewing bacterial growth simply as a biological phenomenon, the scientists use it for information processing," the team explained. The growth curves generated by the bacteria essentially became readable answers to complex medical questions.
This method could eventually bring advanced diagnostics to places that can't afford expensive laboratory equipment. The same approach might also be adapted for monitoring environmental samples, including urban wastewater, or analyzing other medical conditions beyond COVID-19. The researchers are now exploring these possibilities, aiming to develop simple, affordable tools that could work anywhere from small clinics to remote communities. At its core, the study suggests that unmodified living organisms could serve as powerful information-processing systems—turning the natural problem-solving abilities of bacteria into practical medical technology.