It seems that relationships are key even when it comes to bacteria, with research suggesting that health is driven more by how gut microbes interact than the individual species themselves.
The findings, in Science, reveal the importance of dysbiosis—an imbalance in gut microbial communities—and show how interactions within the microbiome can act as a marker distinguishing health from disease.
They also offer a potential explanation for the benefits offered by fecal transplants, which restore entire microbe communities and maintain their healthy interactions rather than focusing on individual species.
Lead researcher Roberto Corral López, PhD, now a postdoctoral associate at the Instituto Carlos I de Física Teórica y Computacional in Spain, said the work could lead to more predictable results from microbiome-based therapies.
“Right now, donor selection is largely based on availability and basic health screening,” he explained.
“Our work opens up the possibility of matching microbial communities based on how their interaction networks fit together, rather than just which species are present.
“That could help us design treatments that are tailored to each patient’s microbiome instead of relying on trial and error.”
An imbalance in gut microbial communities is associated with a wide range of diseases including obesity, diabetes, inflammatory bowel disease, and colorectal cancer.
Previous studies have suggested that health and dysbiosis may represent alternative community states.
However, most attempts to define dysbiosis have set out to identify bacterial taxa or functions that differ between healthy and diseased communities or else assume that reduced diversity is a hallmark of disease.
To provide a more comprehensive understanding, the team developed a metabolically explicit model in which bacterial interactions arise naturally from competition for shared resources and cross feeding.
They captured macroecological patterns and functional redundancy characteristic of real microbiomes, revealing whether microbial communities are dominated by competitive or cooperative interactions.
It showed that healthy and diseased guts were driven more by how the interaction of microbes rather than the individual species themselves.
The microbes naturally split into two distinct patterns and showed health and disease as two fundamentally different ecological states.
Health was associated with a diverse, competitive interactions, while in a disease state the microbes reorganized into more tightly connected consortia.
The team also developed a metric called the Ecological Network Balance Index (ENBI), which measures the relative contribution of positive versus negative interactions and reliably separated health and disease.
When applied to existing data, the ENBI consistently separated healthy individuals from patients with different diseases. For example, the index rose as colorectal cancer progressed.
“This work shows that gut health is not just about which bacteria are present, but how they interact with one another,” said researcher Maria Gloria Dominguez-Bello, PhD, from Rutgers University in New Jersey.
“Treatments are typically based on the idea that you need particular bacteria to be there,” added fellow Rutgers researcher Juan Bonachela, PhD.
“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.”
