The whole gut ecosystem
A dominant butyrate producer with strong anti-inflammatory effects — one of the most consistently health-associated bacteria in the gut.
Butyrate-producing bacteria that help feed the gut lining and dampen inflammation.
A normal gut resident, but specific strains (like adherent-invasive E. coli) can drive inflammation — a classic pathobiont where strain matters more than presence.
Beneficial, fibre-loving bacteria and a common probiotic target; abundant in breastfed infants.
A mucin-degrading species that strengthens the gut barrier and is broadly tied to metabolic health — though its role flips in some conditions.
An oral bacterium that becomes enriched in colorectal tumors, where it appears to actively promote tumor growth and immune evasion.
A toxin producer that overgrows when antibiotics clear its competitors, causing severe diarrhea; a leading healthcare-associated infection.
A notable producer of GABA, the calming neurotransmitter; lower loads correlate with depression and anxiety.
Lactic-acid bacteria found in fermented foods and many probiotics; relatively resilient and generally protective. A key GABA producer.
A common commensal yeast that turns opportunistic under the right conditions; enriched in Crohn’s, where it amplifies inflammatory cytokines in a self-reinforcing loop. Feeds on simple sugar.
A skin-resident yeast surprisingly found in the gut. It’s expanded in Crohn’s, exacerbates colitis in mice via the IBD-linked CARD9 gene, and tracks an unfavorable disease course.
Baker’s and brewer’s yeast — depleted in Crohn’s and positively linked to beneficial butyrate producers. Its relative S. boulardii is used as a probiotic.
The most common gut protist — and the poster child for ‘parasite vs partner.’ Carriers tend to have HIGHER bacterial diversity and leaner, healthier guts, and it’s more common in healthy people than in IBD. Yet some studies link it to IBS. Effects are subtype- and host-dependent.
Whipworm, hookworm and roundworm — the ultimate double-edged organisms. A heavy burden harms, but their immunomodulation is tied to HIGHER diversity and LOWER rates of allergy, autoimmunity and IBD. Controlled helminth exposure has even been trialed as IBD therapy.
The dominant gut virus type — over 90% of gut viruses are phages that infect BACTERIA, not you. They shape which bacteria thrive, defend against invaders, and shuttle genes. Their effect on your health is mostly indirect, through the bacterial community. The least-understood domain in the gut.
The single most abundant virus in the human gut (discovered only in 2014). It infects Bacteroides, is nearly universal, and is essentially benign — used as a marker of human gut/faecal presence.
The leading cause of acute gastroenteritis — the ‘stomach flu’ of sudden vomiting and diarrhea. Highly contagious and self-limiting in healthy people.