Faecalibacterium, which has only one species Faecalibacterium prausnitzii, typically makes up 5 to 20% of the gut microbiome in healthy adults. It is considered one of the most common gut bacteria. Researchers have observed lower than normal levels of Faecalibacterium might be correlated to irritable bowel diseases (IBD) like Crohn's Disease, colon cancer, obesity, and asthma, although more studies are needed to definitively prove this.