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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.
Chapter 10
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.
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.
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.
Chapter 10
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.
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.
Chapter 10
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.