Dr. Ian Marcus, recent Ph.D. from the U.C. Riverside Bourns College of Engineering, wanted to better understand how bacteria impact the environment . So he spent nearly a year building a system that replicates a human colon, septic tank and groundwater and "fed" the colon three times a day during week-long experiments to simulate human eating.

scientists typically study bacteria in an isolated environment under ideal growing conditions. That presents a problem because bacteria typically proliferate in microbial communities with other microorganisms such as archaea, fungi and protozoa.

Marcus set out to solve that problem by creating a simulated environment where the life cycle of bacteria (he used a pathogenic strain of E. coli in these experiments) and the microbial communities they live in can be studied from the human colon to water treatment to groundwater.

In the past, researchers have simulated the gut of humans and synthetic aquatic environments, but no one had combined the two, Marcus says.

"People would give a kind-of-interested-but-definitely-don't-talk-about-it-during-dinner look because we're literally dealing with crap," Marcus said. "It has got the smell. It has got everything."

Human colon replica built by Dr. Ian Marcus. Credit: Alicia A. Taylor

By comparing his finding with those of researchers who worked with bacteria in an isolated environment, Marcus found that the E. coli strain in the microbial community may be less mobile in aquatic environments and more prone to biofilm that than the isolated strain.

E. coli would linger longer in the environment, since biofilm provides a refuge for all the microorganisms within it. When the biofilm matures it sends out bacteria to colonize another surface thus the bacteria could survive in the environment for longer periods of time.

"This means that pathogens could potentially linger longer and over a long period of time travel greater distances in the groundwater," said Marcus.

Marcus worked in the lab of co-author Sharon Walker, an associate professor of chemical and environmental engineering at U.C. Riverside.  Other co-authors were Hailey A. Wilder and Shanin J. Quazi.   Title: "Linking Microbial Community Structure to Function in Representative Simulated Systems" in Applied Environmental Microbiology.