Exploring the Role of Gut Bacteria in Digestion

A team of researchers from the U.S. Argonne National Laboratory has recently published a paper describing thoroughly the structure of bacterial enzymes, which play a fundamental role in human digestion. These bacteria help our digestion system to break down sugar polymers to simple glucose, and therefore better understanding of their structure could help scientists improve the lives of many patients.
 Scientists at Argonne worked together to better understand bacteria and enzymes in the human gut. Pictured (left to right) are Christine Tesar, Kemin Tan, Andzej Joachimiak, Gyorgy Babnigg and Rosemarie Wilton. (Credit: Argonne National Laboratory)
Scientists at Argonne worked together to better understand bacteria and enzymes in the human gut. Pictured (left to right) are Christine Tesar, Kemin Tan, Andzej Joachimiak, Gyorgy Babnigg and Rosemarie Wilton. (Credit: Argonne National Laboratory)

Humans are born without bacteria, yet they inhabit our bodies within seconds of our birth. They live in our mouths, around our eyes, in our digestive systems, under our arms, and in the shoots of our hair. Studies have shown that they congregate in the environments that suit them best: some are in dry places (such our forearms), while others are located in our feet, where it is humid.

Most of the bacteria are helpful – or at least harmless; for that matter, the bacteria in our gut (mostly in the large intestine) in considered beneficial, helping us digest all kinds of food. The team of scientists, led by Andrzej Joachimiak, the director of the Structural Biology Center and the Midwest Center for Structural Genomics at the U.S. Department of Energy’s Argonne National Laboratory, studied these bacteria with great detail.

Previous research studies already established that the bacteria inside our gut influences our maturation, immune system development, metabolism, and production of essential biocompounds. Moreover, it has been proven that a number of diseases are associated with changes in our gut bacteria, or microbiota. The known diseases affected by this phenomenon include diabetes, inflammatory bowel disease, and cardiovascular disease.

Joachimiak, co-author Kemin Tan, and their group recently published an article concerning the structure of such bacteria in the Journal of the Federation of American Societies for Experimental Biology. In their research, they conducted experiments to determine the three-dimensional structure of one of these bacterial enzymes.

The team knew that human cells are responsible for breaking down sugar polymers to simple glucose; however, they were surprised to discover that bacteria affect this process so greatly. The importance of this discovery is that it might help doctors to leverage the bacteria activity to improve the impact of gut organisms on human diseases like diabetes.

According to Joachimiak, there are many practical applications of this type of knowledge. For instance, the medicine prescribed today focuses on human, rather than bacterial cells; in part, it is because we know relatively little about the hundreds of species of bacteria living in and on our bodies. “We target human enzymes with drugs,” said Joachimiak.

Traditional clinicians do not often target bacterial enzymes. “If someone has diabetes, doctors prescribe drugs to control their production of glucose,” Joachimiak says. “We might want to consider whether bacterial enzymes that produce glucose should also be targeted.” Some medications – specifically, antibiotics and antimicrobials – do, in fact, target bacteria, but this arsenal could be greatly expanded if scientists knew more about exactly what these symbiotic companions do inside their hosts.

In its paper, the team claims that our “gut microbiome” (the colony of bacteria that live in our digestive tract) has been co-existing and evolving with us throughout human history, but only recently have scientists devoted time to understanding these tiny, unicellular organisms. Gyorgy Babnigg, who worked with Joachimiak on this project, said that the team determined the structure of about a dozen of these sugar-degrading enzymes, all of which play an important role in helping us with digestion.

“The human body can use starch very effectively; the degradation starts immediately when we chew our food,” Babnigg said. “The di- or tri-saccharides are degraded in the small intestine and the resulting glucose is readily absorbed.” The complexity of the enzymes makes the work of the team more challenging, he adds. “The structures of these enzymes can shed light on their inner workings; this is a growing area of study, and numerous projects aim at sequencing the DNA of these microbes.”

Molecular biologist Rosemarie Wilton, one of the team members, examined how these proteins break apart sugar molecules. “My end of the research yielded some important clues that will help us interpret some of the sequencing data coming out now,” she said. “This is one little piece of the puzzle. It’s a huge and complex system, and these systems are difficult to study because it’s impossible to perfectly replicate the human gut where all of these different species of bacteria live together.”

“This is an area that has only recently been explored,” Joachimiak said, and explains that most researchers have placed emphasis on this area of study only in the last decade. Scientists say now is the time to focus on this type of research, especially considering that bacteria outnumber human cells by at least 10 to one. “There is so much more to know,” concludes Joachimiak.

TFOT covered other research studies regarding bacteria, such as the Weizmann Institute’s study showing that bacteria can anticipate certain future events in their environment and prepare for the upcoming changes. Other related TFOT stories include bacteria that turns carbon dioxide into liquid fuel, developed at UCLA, and the first self-replicating, synthetic bacterial cell, created by JVCI.

For more information about the role of gut bacteria in digestion, see the official press release, published by the Argonne National Laboratory.