Table 1:

Summary of main findings from gut microbiota composition studies in IBS

Microbiota variable	IBS subtype	Summary of finding	References
Alpha diversity	Both	Reduced in cross-sectional samples or samples with high symptom severity	16, 18, 20, 21
Microbiota stability	IBS-C	Larger temporal variability of fecal community than healthy control samples	18
Proteobacteria	Both	Elevated in mucosal community from biopsy samples	18, 19
Streptococci	Both	Elevated in fecal community, positively associated with high symptom severity	16-18
Ruminococci	Both	Elevated in phylogenetic microarray studies, but not reported in sequencing studies	19, 89
Lachnospiraceae	Both	Elevated in fecal community, implicated in reduced fecal hypoxanthine levels	16, 18, 90, 91
Methanobrevibacter smitthii	Both	Functionally implicated in constipation but differentially abundant in very few sequencing studies	89
Alistipes	Both	Bile tolerant bacteria, have been associated to pain	19