Bifidobacteria

Bifidobacteria are gram positive, anaerobic bacteria that are ubiquitous in a healthy gastrointestinal tract. They are protective against intestinal permeability and have been shown to be reduced in CFS patients

One study found that 6-8 weeks of Bifidobacterium infantis supplementation reduced C-reactive protein, TNF-alpha and IL-6 levels in CFS patients. Another found that B. infantis boosted serotonin levels in the brain.

FUT2
Fucosyltransferase 2 enzyme (FUT2) is an enzyme related to intestinal dysbiosis. People who are genetic non-secretors of FUT2 have reduced diversity, richness, and abundance of bifidobacteria.