"There are several indications that the gut microbiota is involved in the onset of FBD [functional bowel disorders], such as dyspepsia and IBS [irritable bowel syndrome]. The gut microbiota participates in gut homeostasis and plays an important role in a number of digestive processes, one of them being gas production: meal substrates that are not absorbed in the small bowel enter the colon, where they may be fermented by colonic bacteria releasing gas. The volume of gas produced depends on the fermentative pathway, and hence the composition of the colonic microbiota. Some data also indicate that the colonic microbiota may modulate motor reflexes and influence gut motility, as the administration of probiotics in patients with constipation accelerates gut transit."
Press Release - Gut microbiota plays important role in functional bowel disorders - The Gut Microbiota For Health Experts Exchange