Skin bacteria communicating, illustration. Many types of bacteria are found on skin, especially associated with sweat glands and hair follicles. They usually cause no problems, although some can cause acne. Bacteria usually only become a problem if they penetrate the skin, for example through a wound or cut. Here, the bacteria are connecting and communicating by chemicals and microtubes, both between bacteria of the same species and of different species (rod-shaped and spherical).