Bacteroidetes
Plain-English definitions of microbiome research vocabulary — the terms you'll see across articles, testing services, and probiotic claims.
One of the two dominant bacterial phyla in the human gut (alongside Firmicutes). Bacteroidetes species are generally skilled at breaking down complex plant polysaccharides and are associated with leaner body composition in some studies. The Firmicutes-to-Bacteroidetes ratio was once considered a key health marker, though its significance is now debated.
Related terms
Firmicutes
The largest bacterial phylum in the human gut, encompassing diverse genera including Lactobacillus, Clostridium, Faecalibacterium, and Ruminococcus. Many important SCFA producers belong to this phylum. An elevated Firmicutes-to-Bacteroidetes ratio has been associated with obesity in some studies, though the relationship is complex and inconsistent.
Microbiome Diversity
The variety and abundance of different microbial species in a given environment. Greater diversity is consistently associated with better health outcomes, while reduced diversity is linked to obesity, inflammatory bowel disease, and other chronic conditions.