A Happy, Healthy Gut Microbiome
Posted by Leanne Kodsman on
The gut microbiome is an exciting field of scientific research, as new studies continue to find links between the composition of the gut microbiome and an individual's overall health (and how this potentially ties in with disease). One of the lingering questions has been curiosity about how, exactly, an individual's microbiome is established. New research addresses this point, looking at the mechanisms used by gut bacteria to develop a healthy, thriving microbiome.
The gut is a happy habitat for bacterial growth - it is warm, moist, and offers an abundance of nutrients. The colonies of "good bacteria" that flourish in the gut are vital partners in helping the body perform important tasks like digesting fiber, extracting nutrients, and preventing disease. How is it that mammals are able to maintain such beneficial partnerships with gut bacteria, while the body typically has such a strong immune and/or illness response to pathogenic bacteria? What makes gut bacteria different?
A Closer Look at Bacteriodes fragilis
New research shows how one species of beneficial gut bacteria is able to harness the body's intrinsic immune response as a way to settle happily in the gut. Researchers looked closely at the Bacterioides fragilis microbe. This particular species is commonly found in the large intestines of a variety of mammals, including humans, and has been shown in previous research to prevent certain inflammatory and neurological disorders in mice (like inflammatory bowel disease and multiple sclerosis). Although there are various strains of B. fragilis, it is notable that healthy people tend to form a long-term relationship with only one strain throughout their lives.
The research team first looked at the specific locations where the bacteria took up residence. B. fragilis tends to cluster together within the thick layer of mucus that lines the gut (near the epithelial cells lining the surface of the intestine), which could be a necessary characteristic that allows for a single species to establish a strong presence.
Next, the team looked closer at the mechanisms that allow the bacteria to create their niche within the gut - they found that each B. fragilis bacterium is encased in a thick carbohydrate-based capsule, which may be a driving force in allowing the bacteria to dominate their niche within the gut.
Triggering the Immune System
Capsules like these are typically related to an immune response in pathogenic bacteria, a "trigger" that will often provoke an immune response. Sure enough, the researchers discovered that antibodies were binding to the B. fragilis capsules in the gut - but, unlike the imminent death that usually awaits pathogenic bacteria, immunoglobulin A (IgA) does not negatively impact most of the beneficial gut bacteria. In this particular case, it seems like IgA actually helped B. fragilis attach to epithelial cells.
The researchers believe the body's immune response is actually helpful to the "good bacteria" in the gut microbiome, allowing the bacteria to thrive - which then helps the host to thrive, as well. The research suggests that the immune system seems to function as more than just defense, and that antibodies can be useful in more ways than simply providing the body with a weapon against pathogens. Future research is expected to explore how to improve colonization by beneficial bacteria, an area of research that could lead to better probiotics and finding ways to use the gut microbiome as medicine for treating illness or disease.
Further Reading & References:
California Institute of Technology. "A gut bacterium's guide to building a microbiome: Unlike invading pathogens, which are attacked by the immune system, certain good bacteria in the gut invite an immune response in order to establish robust gut colonization." ScienceDaily. ScienceDaily, 4 May 2018. ww.sciencedaily.com/releases/2018/05/180504133624.htm.
G. P. Donaldson, M. S. Ladinsky, K. B. Yu, J. G. Sanders, B. B. Yoo, W. C. Chou, M. E. Conner, A. M. Earl, R. Knight, P. J. Bjorkman, S. K. Mazmanian. Gut microbiota utilize immunoglobulin A for mucosal colonization. Science, 2018; eaaq0926 DOI: 10.1126/science.aaq0926
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