The Gut Microbiome: 100 Times Our Genes, Butyrate and a Frozen Stool Ark

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode! The human genome has roughly 20,000 to 25,000 genes, but the gut microbiome carries about 100 times more, making you genetically about 1 percent human. This episode tours the 10 to 100 trillion microbes inside you, which make up as much as 55 percent of the dry mass of stool. The stomach is nearly sterile acid, though Helicobacter pylori survives by wrapping itself in ammonia. The colon holds the densest microbial community ever studied, with 300 to 1,000 species, yet about 99 percent of gut bacteria come from 30 or 40 species, almost all strict anaerobes that die in oxygen. These microbes ferment fibers we cannot digest into short chain fatty acids. Butyric acid supplies about 70 percent of the energy for cells lining the colon, and the gut flora also makes B vitamins and vitamin K. Acting like an endocrine organ, it influences how calories are stored. The episode covers dysbiosis in inflammatory bowel disease, the gut-brain axis along the vagus nerve, gut yeasts, how a microbiome forms by about age two, and how industrial diets and antibiotics are thinning its diversity. Germ-free rodents needed 30 percent more calories to keep the same body weight as normal rodents In inflamed guts, oxygen seeps in, beneficial anaerobes die and Proteobacteria multiply Over 90 percent of the body's serotonin is produced in the gut Gut bacteria in Malawian and Amerindian communities carry different enzyme toolkits than those of people in the United States A 2018 proposal for a global biobank to preserve stool samples from non-industrialized populations