Bacteroides fragilis are anaerobes who colonize the gastrointestinal system. The condition needed to grow is an environment devoid of oxygen. These bacteria are able to produce a capsule to protect them from phagocytosis by the immune system. This bacteria is a gram-- negative rod shaped bacteria and is non-motile. It is found in fecal matter. It competes with other bacteria in the gut for food which is beneficial as it decreases the amount of nutrients available to competing disease producing bacteria to grow in the gut.