Bacteria are present on our skin, in our gut, and in many of the foods that we eat - ALL the time! In fact, there are about 10 times more bacterial cells in and on the body than there are human cells! Most bacteria are harmless, and some are quite helpful. We don't notice them, but we need these bacteria to keep our bodies working normally!
(Hint: Click on regions of the human body to learn more about bacteria living there.)