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Meet your Microbiome: Bacteroidetes

When you get back your GI Map stool analysis one of the first things that is shown is Bacteroidetes and Firmicutes levels. I think of this as a 20,000-foot view of the major population of your gut. The way life forms are named are in this sequence:

1. Domain

2. Kingdom

3. Phylum

4. Class

5. Order

6. Genus

7. Species

Bacteroidetes is a phylum of bacteria that live in your gut. From this point stool analysis will often discuss gut habitants in a Genus and Species. Bacteroidetes accounts for almost 50% of the gut inhabitants.

The other phyla in the gut are Firmicutes, Actinobacteria, and Proteobacteria. Of course, there are other inhabitants in the gut Parasites/Protozoa, Helminths, Yeasts, and Viruses.

Bacteroidetes, however are the largest phylum of gram-negative bacteria in the gut and cornerstone of a healthy gut. They account for 50% of the species in the human gut whereas Firmicutes accounts for almost the rest. Bifidobacterium is a member of the Actinobacteria phylum and is a crucial Genus related to gut health.

Some other facts about the members of Bacteroidetes:

● Represent 7000 different species

● Bacteroidetes consist of commensal, mutualist, and even pathobionts (pathogenic) organisms.

● Bacteroides (a genus in this phyla) is atypical glycan degrader with an unusual ability to recognize a dozen plant and host polysaccharides and degrade glycans meaning they are good at digesting mucus, starches, and pectin’s.

● One species in this phylum… Bacteroides fragilis. Has been associated with colorectal carcinogenesis due to its release of Bacteroides fragilis (Toxin)

● It has been suggested that Bacteroidetes members Klebsiella and Prevotella are in abundance in Major Depression patients and may be linked to depression.

● Bacteroidetes member Prevotella copri dominance has been demonstrated to induce a TH17 cell dependent arthritis in intestinal microbiota humanized mice in contrast Prevotella histolytica has been shown to suppress the development of arthritis, lowering inflammation

● Prevotella abundance seems to be associated with a high fiber diet

● Bacteroides abundance is associated with consumption of animal fat and protein reich diets

● Obese people have relatively more firmicutes as do rodents on a high fat diet.

● Weight loss has been associated with increases in Bacteroidetes in mice.

● Fecal transplants in Autistic Spectrum Disorder patients that resulted in with a in improved richness of Bifidobacterium, Prevotella, and Desulfovibrio among other taxa increased improved ADS symptoms up to 8 weeks after transplant (kang

This foundation will continue to grow, but we know we can sometimes modify, adjust, and influence the microbiome by herbal medicine, foods we choose, and also from medications, travel, pregnancy, and aging.

Regardless with so many important members and with an influence on immune, metabolic, and mental health, getting to know Bacteroidetes will likely lead us to greater understanding of the role our gut health plays in overall heath.


Gibiino, G. (2018). Exploring Bacteroidetes: Metabolic key points and immunological tricks of our gut commensals. Digestive and Liver Disease, 635-639.


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