" the time of writing, there is only one other probiotic bacteria species that is as well researched as the two mentioned above: E. coli Nissle 1917. This strain of E. coli was first isolated from the faeces of a soldier returning from the Balkan War. All the soldier’s comrades had suffered severe diarrhoea in the Balkans, but he had not. Since then, many studies have been carried out to show that this bacterium can help with diarrhoea, gastrointestinal disease, and a weakened immune system. Although the soldier died many years ago, scientists continue to breed his talented E. coli in medical laboratories and package it up for sale in pharmacies so it can work its wonders in other people’s guts. "

― Giulia Enders , Gut: The Inside Story of Our Body’s Most Underrated Organ