Gut diversity

The human gut hosts an array of microbes that form a complex community beginning shortly after birth. These microbes prime the immune system, help extract nutrients from the diet and offer protection against pathogens. Decades of research have shown that individuals who suffer from inflammatory bowel diseases (IBD) or other systemic disorders tend to have far less variety of gut microbes compared to healthy individuals. Yet it remains unclear to what extent the difference in microbial diversity is the cause of the disease or a consequence of it.

In 2023, a study suggested that the usual teamwork between different kinds of microbes breaks down during disease. Many microbes depend on each other to provide certain nutrients, while others can survive on their own. It could be that people with IBD lose most of the ‘dependent’ microbes and retain those that are more self-sufficient and thus able to survive in the stressed and deteriorating gut environment.

To test this hypothesis, Veseli et al. – who are part of the research group that performed the 2023 study – developed a computer program to quantify self-sufficient gut microbes in large numbers of stool samples collected from healthy individuals and patients with IBD. This revealed that individuals with IBD had higher numbers of self-sufficient microbes, while healthy people also harbored microbes that depended on others for the provision of essential metabolites. External disruptions to the gut homeostasis, such as antibiotics, resulted in a similar selection for independent microbes.

These findings support the idea that changes in the gut microbiome are more likely a by-product of disease, rather than its cause and offer important ecological clues for microbial therapies that aim to restore gut health. While this perspective assigns a more neutral role for gut microbial communities in non-transmissible diseases, more research is needed to see if an enrichment of self-sufficient microbes could negatively influence disease progression.