Vegetative Stages and Spore Formation

Although vegetative bacteria may survive low—even freezing— temperatures, they can be killed by high temperatures. For example, pathogenic bacteria can be killed during proper cooking. Some types of bacteria, however, have the ability to change into a different form, called a spore. The spore’s thick wall protects the bacteria against unfavorable conditions, such as high or low temperature, low moisture, and high acidity.

While a spore cannot reproduce, it is capable of turning back into a vegetative organism when conditions again become favorable. For example, bacteria in food may form a spore when exposed to freezer temperatures, allowing the bacteria to survive. As the food thaws and conditions improve, the spore can turn back into a vegetative cell and begin to grow in the food.

Since spores are so difficult to destroy, it is important to cook, cool, and reheat food properly.

Conditions that Support the Growth of Microorganisms

All microorganisms, except viruses, are able to grow in food if the conditions are right. To grow, microorganisms need food, water, appropriate temperatures, oxygen, and proper pH. Therefore, you must control these necessities to control their growth of microorganisms.

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