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They're Everywhere: Bacteria

Author(s): Nancy Moreno, PhD, and Barbara Tharp, MS.

The Science of Bacteria

In this activity, students observed the following properties of bacteria and how it relates to food-borne illnesses.

  • Bacteria are everywhere. Bacteria are the most numerous of all things living on our planet. However, they are so tiny that it is not possible to see a bacterium (a single bacteria) without the aid of a microscope. Most bacteria must be magnified at least 400 time to be seen with the naked eye. Each bacterium consists of one cell capable of reproducing very rapidly. In fact, one bacterium cell can produce millions of others in just one day. Bacteria are everywhere. They can be found on nearly every surface—including skin. They also are found in the digestive tract, the mouth, throat and intestines. However, they are not found anywhere inside the tissues of the body or in the blood of healthy persons.
  • Bacteria need food to grow. In the laboratory, bacteria are grown in nutrient agar, a medium derived from algae which provides bacteria with the sugars and nutrients needed to survive in a petri dish.
  • Bacteria are important decomposers, but they also can cause many different diseases. Bacteria are essential in many ways. They are important decomposers in almost all ecosystems. Photosynthetic bacteria (also known as blue-green algae) are vital producers in aquatic ecosystems. Bacteria in the intestines of animals help break down some large food molecules during digestion. However, bacteria also can cause serious problems with food. Since they are everywhere, it is easy for bacteria to contaminate food and cause it to spoil. The slime you see on food that has been in the refrigerator too long is made of clumps of bacteria and, sometimes, fungi as well. Eating spoiled food can make humans and other animals sick.
  • Bacteria are a major source of food contamination. Bacteria can be transferred to food when people do not wash their hands after using the bathroom, changing a diaper or playing with pets. Some foods, especially meats, can have bacteria on their outside surfaces. These bacteria can be transferred to other foods if utensils and cutting boards used in food preparation are not washed with soap and water.

Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

My Health My World: National Dissemination
Grant Number: 5R25ES009259
The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698, R25ES06932