The fecal microbiome is comprised of the microbes, including bacteria and viruses, that naturally live in the feces. Diet, environmental factors, and antibiotics can alter the fecal microbiota. In rare cases, patients with C. difficile colitis, a condition where much of the normal, healthy bacteria in the colon has been depleted, a fecal microbial transplantation, also called bacteriotherapy, can be performed to replenish the microbiome.