Bacteria on tongue. Coloured scanning electron micrograph (SEM) of part of a mammal tongue filiform papillae and taste bud, with bacteria (green) present. Filiform papillae are found toward the back of the tongue. Tiny bumps called papillae give the tongue its rough texture. Thousands of taste buds cover the surfaces of the papillae. The mouth and other parts of the digestive tract contain many bacteria, most of which are non-pathogenic and play a vital role in maintaining a healthy digestive system.