Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the third of four Science Objects in the Science of Food Safety SciPack. It explores how bacteria live in close concert with humans. Bacteria are masters at exploiting a variety of niches in the human body and live in huge colonies in places such as the skin, intestines and mouth. Most of these bacteria are harmless to the human body, and many are important in assisting its normal, healthy functioning. Disease in humans results when organisms such as bacteria interfere with the normal operation of the human body, most commonly foreign organisms entering the body. The human body has many mechanisms to protect itself against outside organisms that may interfere with its normal operation.
Bacteria that gain entrance to the body may form colonies in preferred organs or tissues, emitting harmful toxins as waste products. If the body's immune system cannot suppress a bacterial infection, an antibacterial drug may be effective—at least against the types of bacteria it was designed to combat. Viruses invade healthy cells and cause them to synthesize more viruses, usually killing those cells in the process.