1. Chapter 10
Section 2 Bacteria’s Role in the World
Bellringer
Are harmful bacteria more of a problem or less of a problem to people now than they were 200 years ago? Name some major historical events involving the spread of bacteria. How would your life change if you had to worry about getting clean water each day?
Record your answer in your science journal.

2. Chapter 10 Objectives Explain how life on Earth depends on bacteria.
Section 2 Bacteria’s Role in the World
Objectives
Explain how life on Earth depends on bacteria.
List three ways bacteria are useful to people.
Describe two ways in which bacteria can be harmful to people.

3. Good for the Environment
Chapter 10
Section 2 Bacteria’s Role in the World
Good for the Environment
Nitrogen Fixation Nitrogen-fixing bacteria take in nitrogen from the air and change it to a form that plants can use.

4. Good for the Environment, continued
Chapter 10
Section 2 Bacteria’s Role in the World
Good for the Environment, continued
Recycling Decomposer bacteria break down dead plant and animal matter, which makes nutrients available to other living things. Organisms like this are called saprophytes.
Cleaning Up Using microorganisms, such as bacteria, to change harmful chemicals into harmless ones is called biomediation. Biomediation can be used to clean up hazardous waste and oil spills.

5. Chapter 10 Good for People
Section 2 Bacteria’s Role in the World
Good for People
Bacteria in Your Food Many common foods, such as cheese, yogurt, and sour cream, are made with the help of bacteria.
Making Medicines Medicines used to kill bacteria and other microorganisms are called antibiotics. Many antibiotics are made by bacteria.

6. Good for People, continued
Chapter 10
Section 2 Bacteria’s Role in the World
Good for People, continued
Insulin In the 1970s, scientists discovered how to put genes into bacteria so that the bacteria would make human insulin.
Genetic Engineering changes the genes of bacteria, or any other living thing. Scientists can now engineer bacteria to make many products, such as insecticides, cleansers, and adhesives.

7. Chapter 10 Harmful Bacteria
Section 2 Bacteria’s Role in the World
Harmful Bacteria
Pathogenic bacteria are bacteria that cause disease by getting inside a host organism and taking nutrients from the host’s cells.
Diseases in Other Organisms Bacteria cause diseases in other organisms as well as in people. Pathogenic bacteria attack plants, animals, protists, fungi, and even other bacteria.