Aside from bacteria that the body encounters in the environment, the three major species of bacteria living on the skin are Propionibacterium, Corynebacterium and Staphylococcus, according to The Scientist. They reside within the glands, follicles, invaginations and appendages.
Bacteria found on the body serve several purposes, including defending against pathogenic invaders, building immunity against pathogens and protecting against excessive inflammation, says The Scientist. Bacteria also alter the immune response of body cells and affect the bacterial existence in the surrounding environment. Bacteria that negatively affect the body cause inflammation and illnesses, such as staph infections.
Diversity of the environment provided by the human body prompts changes within existing bacteria. Propionibacterium lives in oily or sebaceous areas close to the neck, head and trunk of the body, according to The Scientist. Blemishes on the skin, attributed to P. acnes, are characterized by the presence of sebum, consisting of lipids secreted by exocrine glands. Corynebacterium resides in creases, such as between the breasts, between the toes and at the elbows. Staphylococcus exists in broad, flat areas mainly exposed to the environment, such as on the forearm or leg.
Bacteria affect the immune response uniquely, reports The Scientist. Distributed across the skin in a manner that is not uniform, bacteria also exist in the layers below the epidermis or top layer of the skin. Those strains that are beneficial sometimes thrive by inhibiting other malicious forms, such as gram-positive species of bacteria.