Normal Flora refers to the collection of organisms that live on or within the bodies of animals and plants. These organisms are made up of bacteria, fungi and protozoa. They do not cause diseases in healthy individuals and either have a commensal or mutualistic relationship with their host. In some cases when the immune response of the host is down, some of these organisms might act as opportunistic pathogens and cause diseases. In humans the the normal flora which is also called microbiota is found in many places including the skin, the gut and in oral cavities. Although the organisms that make up the microbiota are found on all surfaces that are in some contact with the environment, the majority of bacteria live in the large intestine.