A researcher at the University of California Riverside spent a year building a model of a human colon out of commonplace materials, then "fed" it with real food, to study how bacteria spreads from feces into the water supply. "I hadn't seen any research done that used a model colon to find out what happened downstream" said Ian Marcus, the recently graduated UC Riverside PhD student who built the system, told The Verge. What Marcus and his colleagues found out is worrisome: when mixed with human fecal matter, disease-causing e. coli bacteria can survive longer in groundwater than previous studies indicated. "People might think that if there's an outbreak that's been contained, 'we're good,' but it turns out the bacteria could stay around longer and linger," Marcus said, noting that the problem was likeliest to occur in rural water supplies such as wells as reservoirs.

Marcus built the colon out of a 20-inch-long glass tube and rubber stoppers. He and his teammates filled it with real, beneficial, human intestinal bacteria — the kind that helps us digest food and doesn't make us sick — and added a food solution to simulate digestion. Then they took some of the resulting mixture out and put it in another chamber simulating a septic tank. Later, they added harmful, illness-causing e. coli bacteria to the mix. What they found was that although the e. coli did not spread as far as it did in previous simulations, it was more likely to form a biofilm, a type of sticky network of bacteria cells that can live longer than bacteria cells on their own. This biofilm could then pass disease on through water pipes over a longer period of time. "It can, in theory, move along water pipes," Marcus said. He and his colleagues recently published a paper on their results in the journal Applied and Environmental Microbiology.

Marcus cautioned that the results were obtained in a laboratory setting and that they shouldn't be used to generalize when it comes to the interplay between all septic and groundwater systems around the world or the US. However, he maintains that the system he and his colleagues built is more accurate than previous systems for the purpose of testing how bacteria spreads from the human gut through water pipes, because the UC Riverside colon mimicked the dehydration function of an actual human colon more precisely than others (the fact that the actual colon removes water as it breaks down food), and that it used a more "Western" type of food source. "I saw that other model colons used a protein powder mixture, but I used a mixture that's much more chunky," Marcus said, adding that he had to feed the colon "three times a day," the same number of times that humans are supposed to eat.