The human gut microbiome has a close connection to our well-being, and it has the potential to be used as a biomarker of health, and might be harnessed to treat disease. The gut microbiome can also hold trillions of microbial cells, and one person’s microbiome can be very different from another’s, even when both people are healthy. But scientists are learning more about the ways that the microbiome can be used to identify disease or follow the course of an illness.
Reporting in Science, researchers have shown that the ecological states of the microbiomes of healthy people differ from those with diseases. This study has focused on the effects of bacterial communities, rather than individual microbes, and has shown that patterns of competition or cooperation among those communities can form ecological states that vary between people in good or poor health.
"Instead of asking which bacteria are there, we started asking how they are related to other bacteria; that change in perspective allowed us to see health and disease as two fundamentally different states of the gut microbiome,” explained co-senior study author Juan Bonachela, an associate professor at Rutgers University.
In this study, the researchers created a tool called the Ecological Network Balance Index, (ENBI), which determines if the communities in a microbiome tend to have competitive or cooperative interactions. The competitive ecological state was linked to good health, with a diverse group of microbes that help keep each other under control. But the cooperative state was associated with poor health, and characterized by small groups of bacteria that worked closely together.
This tool was applied to existing data, which confirmed that it could identify those who are healthy, or those with various diseases. For colorectal cancer patients, EMBI increased as the disease worsened. It may be possible to follow the trajectory of a disease by monitoring a patient’s microbiome (through stool samples), for example, the researchers suggested.
Cooperative interactions in the microbiome can lead to the formation of tightly linked groups that may dominate, and interfere with normal gut function, noted study co-author Maria Gloria Dominguez-Bello, a professor at Rutgers.
“This gives us a new way to think about what goes wrong in the microbiome," added study co-author Martin Blaser, director of Rutgers Health's Center for Advanced Biotechnology and Medicine. "Instead of focusing on individual microbes, it shows that disease emerges when the entire system shifts. That opens the door to earlier detection and more targeted interventions."
This work may also help explain why probiotic treatments don’t always work: because improving gut health may not just be about introducing one or two strains of beneficial microbes.
"Treatments are typically based on the idea that you need particular bacteria to be there," Bonachela said. "But if that is not the issue, if the issue is that key relationships are missing, then just adding the bacterium does not make a difference; it is necessary to recreate those relationships."
Fecal transplants could be more effective because they are more likely to transfer whole communities of microbes, added Bonachela.
"We are trying to understand how these systems work so we can make a real difference in people's lives," Bonachela said.
Sources: Rutgers University, Science
